I'm interested in knowing whether there are any legal issues (e.g., copyright infringement) in posting solutions to problems of a (paid) textbook.  I have mentioned these problems in class and did not have the time to thoroughly solve them on the blackboard. I thought about typing up the solutions with an extended discussion on each problem and the concepts employed. However, before I do that, is there any legal action about which I should be concerned? More specifically, I'm thinking about typing them up in Jupyter Notebook-style and was planning on putting those up on a public Github repository.  I had initially typed up the problems as well, but decided to reference to the exercise number in the book, as the "wording" problem itself may be proprietary.  I'm aware that the book has a paid solutions manual to which I don't have access.

Recently, I have worked out a solution manual for a book.   I have not found on the Internet any existing complete solution manual for this book.  Since the solution manual of mine contains every exercise given in the book, my question is: In order to publish or distribute publicly this manual, do I have to first request the consent of the publisher of the book?  [Editors note: A solution manual is an accompaniment to a textbook that provides the answers and/or techniques to solve the exercises given in said textbook. Other names for these include: answers keys and teacher's handbook.]


Is there any way to show the number of selected vertices in Edit Mode?

Is there a way to get Statistic info in Blender? Or heads up display? Like when I select a group of vertices, I need a way to know how many vertices are selected and How many polygons "or triangles my scene has.


The problem involves placing the maximum number of bricks over one another before the system falls off. Each brick is displaced with respect to one in contact by distance $d$. The mass of each brick is $m$. I have to find the maximum number of bricks I can place in the above manner.  I am trying to place the bricks this way:  xxxxxx   xxxxxx     xxxxxx       xxxxxx    I am a little rusty on my mechanics problem solving, so a bit unsure how to proceed. I think I have to solve this by balancing the torques but not sure about what point and what kind of forces I have to include in the calculation. I can find the centre of mass of the system but then what forces will be considered?  Any help is appreciated. Thanks!  EDIT: I see that it is marked duplicate but it is not. The linked thread is finding the maximum overhang with N bricks, mine is different.

I want to stack some boxes which are 14" x 10" with some 12" records inside. This means that there will be a 2" overhang outside of each box.    I know that to have an item to balance on a edge 50% of an item needs to be supported. So I think I'm safe to load the boxes in this way.   If I were to stack boxes loaded in this way on top of each other is there a limit to how high they can go?


Let $A\in M_3(\mathbb R)$ which is not a diagonal matrix.Let $p$  be a polynomial in one variable with real coefficients & of degree 3 such that $p(A)=0$.  Can we conclude that $p=cp_A $ where $c\in \mathbb R $ and $p_A$ is acharacteristic polynomial of $A$?If not  what kind of roots(real/complex) p should have  in order to make such a conclusion.

Let $A\in M_3(\Bbb R)$ which is not a diagonal matrix. Let $P$ be a polynomial (in one variable), with real coefficients and of degree 3 such that $P(A) = 0$. Pick out the true statements:  a. $P = cP_A$ where $c \in\Bbb R$ and $P_A$ is the characteristic polynomial of $A$;  b. if $P$ has a complex root (i.e. a root with non-zero imaginary part), then $P = cP_A$, with $c$ and $P_A$ as above;  c. if $P$ has a complex root, then $A$ is diagonalizable over $\Bbb C$.  I guess b and c are true although I am unable to disprove a. Because A could satisfy $(X-A)$ but this is not a polynomial. Now if $P$ has a complex root, then its conjugate too is its root as the polynomial has  real coefficients. As we all know An odd degree polynomial has always a real root, what we have is three distinct roots. Since $A$ satisfies the polynomial the only difference between the characteristic polynomial and $P$ has to be a constant.


How to proof that the $k$th moments of random variable $X\backsim N(0, \sigma^2)$ which is:  $$ E(X^k) =  \begin{cases} \sigma^k(k!!) & \text{for k even;}\\ \ 0 & \text{for k odd} \end{cases} $$  I started from the basic definition of the $k$th moments:  $$E(X^k) =\int_{-\infty}^\infty x^k\frac{1}{\sqrt{2\pi}\sigma}e^{- \frac{x^2}{2\sigma^2}}dx$$  What kind of integration techniques that could solve this equation?

I would like to learn how to calculate the expected value of a continuous random variable. It appears that the expected value is $$E[X] = \int_{-\infty}^{\infty} xf(x)\mathrm{d}x$$ where $f(x)$ is the probability density function of $X$.  Suppose the probability density function of $X$ is $$f(x) = \frac{1}{\sqrt{2\pi}}e^{\frac{-x^{2}}{2}}$$ which is the density of the standard normal distribution.  So, I would first plug in the PDF and get  $$E[X] = \int_{-\infty}^{\infty} x\frac{1}{\sqrt{2\pi}}e^{\frac{-x^{2}}{2}}\mathrm{d}x$$ which is a rather messy looking equation. The constant $\displaystyle\frac{1}{\sqrt{2\pi}}$ can be moved outside the integral, giving  $$E[X] = \frac{1}{\sqrt{2\pi}}\int_{-\infty}^{\infty} xe^{\frac{-x^{2}}{2}}\mathrm{d}x.$$  I get stuck here. How do I calculate integral? Am I doing this correctly this far? Is the simplest way to get the expected value?


I had taken a multiple choice business test the other day and the question was the following:     1. In Microsoft Word, the scissors function would be used to:       A) Cut or select certain information        B) Bolding a word       C) None of the above     I believe that the "or" in answer A) signifies that the scissor function is capable of both a cut and a select operation, whereas my teacher believes that it means one or the other and since the scissor function is capable of a cut operation A should be the correct answer.   I chose C) "None of the above" and I am considering escalating my complaint to student services.  Some relevant information may include that the Microsoft office being used by this class is of 2003. It is also a grade 9 class.  *Below is a link to the follow up of what happened at student services incase anyone is interested:

My wife and I are playing a game where you roll dice and move so many spaces in a grid "vertically or horizontally".   In the use of English it is very common to say, this or the other when it comes to making a choice  (exclusive or). Now I know that "or" can also be inclusive, for example "she couldn't read or write", or can be clearly used as an xor "you either come or not" making the statement true for only one of the options but not both.   My issue is where it is not clear whether it is an inclusive/exclusive or, the best example being our game.   I argue that you can move in either direction (inclusive) and the normal use of this conjunction in English should be inclusive unless specified otherwise.   Is this right?


I have been contacted by someone who says we are half sisters due to our DNA match. Our DNA is 1,781 which apparently is a high match. Would this make us half sisters? I am an only child and she is adopted.

Given two tests that share some cM of autosomal DNA, how can I easily find the predicted relationships that such shared cM would suggest? For example, a 2,200 cM match suggests it could be either: grandparent, half-sibling, or grandchild.


I am going to cite a research article which also has useful supporting data by authors in their website.   How can I add the link into Bibtex?  Or do I have to cite the supporting data link as an individual reference?

I'm using bibtex for my bibliography in LaTeX. I have some URL's I need to cite in the paper. How do I add URLs into the .bib file?  A typical section in my .bib file looks like this:  @conference{eigenfacepaper,   title={{Face recognition using eigenfaces}},   author={Turk, M. and Pentland, A.},   booktitle={Proc. IEEE Conf. on Computer Vision and Pattern Recognition},   volume={591},   year={1991} }   I tried some misc sections in bibtex but they don't show up in my document.


Context  I am migrating a WordPress website from a Plesk server to a cPanel server. Before I change the nameservers to point to the new website, I would like to test that everything is ok (e.g., database, files, etc...).  Problem  I cannot visit the migrated website if the nameservers are not set. I tried typing the IP directly in my browser, but of course it didn't work, since there are many websites hosted in the same server.  So I guess my question is: How can I access the website before the new nameservers are set? Is it even possible?

I have a few websites that I need to move to a new server - how would I test that they work before switching DNS? What URL would I navigate to?


Let $n > 0$ and let $a_{n-1}, ..., a_0$ be integers. Prove that, if $x^n + a_{n-1}x^{n-1} + ... + a_0 = 0$ has a rational root, then such root is an integer.   I understand that posting questions without showing your work is frowned upon, but I don't know where to start with this one.. thanks in advance.

Let $P \in \mathbb{Z}[x], P(x) = \displaystyle\sum\limits_{j=0}^n a_j x^j, a_n \neq 0$ and $a_0 \neq 0$; if $p/q$ is a root of P (with p and q coprimes) then $p|a_0$ and $q|a_n$  I've managed to prove the first part ($p|a_0$) and I suppose I'm not far from proving the second, though I'd really like some feedback since I'm just starting with making proofs of my own.  Proof:  $P(x) = a_n(x-p/q)\displaystyle\prod\limits_{j=2}^n (x-r_j)$, with $r_j$ being the other n-1 roots of P(x).  It follows that $a_0 = a_n(-p/q)\displaystyle\prod\limits_{j=2}^n (-r_j)$  Then, $-p/q|a_0$ and obviously $p/q|a_0$. Rephrasing, $a_0 = l\frac{p}{q} = \frac{l}{q} p$ with $l \in \mathbb{Z}$.  This implies $p|a_0$ if $l/q \in \mathbb{Z}$, but this is trivial since $q|lp$ and q and p are coprimes, so $q|l$.  Therefore, $p|a_0$.  As for the second part, we want to see that $q_i|a_n \forall i \leq n$.   We define $d$ as the least common multiple of $\{q_1, q_2,...,q_n\}$. Then, $q_i|a_n \forall i \leq n \iff d|a_n$.  Also, it follows that $d|\displaystyle\prod\limits_{j=1}^n q_j$, so we want to see that $a_n = l \displaystyle\prod\limits_{j=1}^n q_j$ with $l \in \mathbb{Z}$. Here's where I have my doubts with the proof as I have no way to show that l is indeed an integer.  Rearranging the previously given equation for $a_0$:  $a_n = a_0 \displaystyle\prod\limits_{j=1}^n \frac{-q_j}{p_j}$  Using the previous reasoning, as $p_i|a_0 \forall i \leq n$, then $a_0 = k \displaystyle\prod\limits_{j=1}^n p_j$.  Replacing $a_0$:  $a_n = k \displaystyle\prod\limits_{j=1}^n -q_j$, which is equivalent to $q|a_n$ as shown earlier.


I double click on a jpg file and see this -     There's a PPC-only rev of this software on my Mac, but it's on a different boot drive, a drive with older OS. The startup drive is running Yosemite and has a new version of this software. If I open the app first, all is fine, but is there any way to tell the system that this current rev is my 'main' image app?   FWIW, On a desktop MacPro 5.1, with multiple boot drives.

I have somehow managed to replace the default movie player, with my FTP client. I'm not sure how that happened, but now every time I double click a movie file in Finder, my FTP client launches.  Can someone tell me how I can go about changing the default application that launches for certain file extensions?


Starting from the axiom of choice and passing the lemma of Zorn we arrive at the well-ordering theorem which states that for every set $X$ there exists a well-ordering with domain $X$.   I am aware that possibly nobody will ever be able to construct an explicit well-ordering of $\mathbb R$. There are in fact enough questions to be found here on math.stackexchange.com  But what about the "next best thing": an explicit (=constructed) well-ordering of $\mathbb Q$?

A well-known mathematical fact is that the rational numbers are countable, i.e. there is a bijective function  $$f:\mathbb{N}\rightarrow \mathbb{Q}$$  I am interesting in making a list of all explicit such bijections since each one that I know have a different philosophy behind it.   This is one of the more counterintuitive facts about infinite, at least when one enters inside set theory. When I explain this in the first time to anyone, he/she is surprised. Thus I think  it will be useful for showing the fact in a more clear manner or as possible exercises to show alternatives ways with respect to the standard one.


For the fair cutting of a cake into n pieces for n people, is it sufficient for one person to cut the cake, and for them to get the last pick of piece?  If any one piece is bigger than 1/n, another person will take that piece. If any one piece is smaller than 1/n, then the cutter may end up with that piece. Therefore the cutter has an incentive to cut the cake fairly.   Is this correct?

This is a problem that has haunted me for more than a decade. Not all the time - but from time to time, and always on windy or rainy days, it suddenly reappears in my mind, stares at me for half an hour to an hour, and then just grins at me, and whispers whole day: "You will never solve me..."  Please save me from this torturer.  Here it is:  Let's say there are two people and a sandwich. They want to share the sandwich, but they don't trust each other. However, they found the way how both of them will have a lunch without feeling deceived: One of them will cut the sandwich in two halves, and another will choose which half will be his. Fair, right?    The problem is:  Is there such mechanism for three people and a sandwich?    EDIT: This was roller-coaster for me. Now, it turns out that there are at least two books devoted exclusively on this problem and its variations:          Yesterday, I was in a coffee shop in a small company. We ordered coffee and some chocolate cakes. As I was cutting my cake for my first bite, I felt sweat on my forehead. I thought, 'What if some of my buddies just interrupt me and say: Stop! You are not cutting the cake in a fair manner!' My hands started shaking in fear of that. But, no, nothing happened, fortunately.


In speech .exe translates to dot e-x-e. In writing, however, should one say an .exe or a .exe?

In the following example, is it appropriate to use a or an as the indefinite article, and why?     He ate __ green apple.   I know that in the case of just "apple", it would be "an apple," but I've heard conflicting answers for "green apple," where the noun is separated from the article by an adjective.  Also, which is more appropriate in this case:     He ate  __ enormous Pop-Tart.


i am fairly new to python, and this is the first hurdle i came across. Here is what's happening: from random import randint  empty = [[0]*9]*9  def randomboard():   board = empty   for x in range(0,8):     for y in range(0,8):       nextInt = randint(0,29) - 20       #nextInt = 0 if nextInt < 0 else nextInt       board[x][y] = nextInt   return board  def printboard(board):   for x in range(0,8):     print(board[x])   print("----")  printboard(empty) printboard(randomboard())  The Output is the following:  [0, 0, 0, 0, 0, 0, 0, 0, 0] [0, 0, 0, 0, 0, 0, 0, 0, 0] [0, 0, 0, 0, 0, 0, 0, 0, 0] [0, 0, 0, 0, 0, 0, 0, 0, 0] [0, 0, 0, 0, 0, 0, 0, 0, 0] [0, 0, 0, 0, 0, 0, 0, 0, 0] [0, 0, 0, 0, 0, 0, 0, 0, 0] [0, 0, 0, 0, 0, 0, 0, 0, 0]  [3, -5, -5, -4, 7, -13, -15, -1, 0] [3, -5, -5, -4, 7, -13, -15, -1, 0] [3, -5, -5, -4, 7, -13, -15, -1, 0] [3, -5, -5, -4, 7, -13, -15, -1, 0] [3, -5, -5, -4, 7, -13, -15, -1, 0] [3, -5, -5, -4, 7, -13, -15, -1, 0] [3, -5, -5, -4, 7, -13, -15, -1, 0] [3, -5, -5, -4, 7, -13, -15, -1, 0]   What the Code should do: Create an Empty 9x9 board. Fill it with random values. Then print the result. As you can see, the first axis keeps repeating, even though i feel like this should not be the case and i can only try to fathom why it is. Here are a couple of possibilities: -The RNG Seed resets after every iteration of the first loop: I wouldn't even know what to do in this case, and it would seem very unintuitive for this to happen. -I have been doing something weird during the construction of the random list.Possibly some false syntax, that i have been taking over from java: I have been looking into other code examples, and the code snippet still seems good to me. Maybe i'm not seeing something, that you do. -The printboard function just prints the first row over and over: I already tried to substitute the funtion for "print(board)", but that also returns the repeating list. -Something totally different, that i have been overlooking At this point, i'd really appreciate your help. Thank you in advance!

I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?


I have a brand new System76 laptop w/15.04, 250G SSD as root partition. I was playing around with pycharm, doing a tutorial when i get a pop-up saying no disk space remaining. I close out of pycharm and open file manager, sure enough, my ssd is full. I've rebooted, but still have my root part full.  How do i find out whats filling it up and clear it out??  UPDATE: I used a 'du -k / | sort -n' to find the largest files being used on the disk, then deleted them.

I was wondering how do you know where the largest files in my system are stored.  For example---  Disk Space Used: 1GB Java: 500MB Java Percentage: 50% maybe represented in a pie chart. Maybe?  I know this maybe a feature overkill. I sometimes forget having stored things and wonder why my disk is so full.   So basically a command that will allow me to run on the file system and provide me with information on disk space used.  Please and thank you.


I have been one of the co-authors of a published paper 8 years ago. In those years I was an undergrad student. So, I had no significant scientific contribution to this paper. I have just finished my Ph.D. and I do not want this paper listed in my publications.   Is it possible to remove my name from this paper via a correction?  Clarification: I have concerns about the quality of this work. It was carelessly written and the quality is low. So I do not want my name to come together.

I managed to successfully publish my old bachelor thesis in a good quality national journal in my country. However, I am thinking of retracting the article due to certain circumstances. First, I felt really embarrassed by the low quality research methodology used in my bachelor thesis. I only used simple correlation in my research. After it was published, I realized that the journal editor team forgot to include a reference in that article because they were rushing me throughout the editing process. I informed them about their mistake and it seems that they have done nothing to fix the problem. I became a bit annoyed because the editor team has never made this problem in the past.  I felt that it would be better for me to simply ask for retraction to solve this issue, but I am a bit afraid of negative consequences in the future. Is it okay to do this? I am really interested of entering the academic world in the future.


Is there any fast (and nice looking) way to remove an element from an array in Java?

Given an array of n Objects, let's say it is an array of strings, and it has the following values:  foo[0] = "a"; foo[1] = "cc"; foo[2] = "a"; foo[3] = "dd";   What do I have to do to delete/remove all the strings/objects equal to "a" in the array?


I'm trying to install Trelby on my Ubuntu 16.10, but I'm getting a dependency error for Python. How do i get past this error?

Trying to install trelby by using sudo dpkg -i trelby_2.2_all.deb produces this error:  Selecting previously unselected package trelby. (Reading database ... 267174 files and directories currently installed.) Preparing to unpack trelby_2.2_all.deb ... Unpacking trelby (2.2) ... dpkg: dependency problems prevent configuration of trelby:  trelby depends on python-wxgtk2.8; however:   Package python-wxgtk2.8 is not installed.  dpkg: error processing package trelby (--install):  dependency problems - leaving unconfigured Processing triggers for gnome-menus (3.13.3-6ubuntu3) ... Processing triggers for desktop-file-utils (0.22-1ubuntu5) ... Processing triggers for mime-support (3.59ubuntu1) ... Errors were encountered while processing:  trelby   It clearly looks like a dependency issue, but I don't know how to resolve this.  Any ideas?


When you post an article on the arXiv, it gives the poster a link for co-authors to claim authorship of the paper. I have claimed authorship for most of my articles but some in the beginning of my career were posted by senior collaborators and I have not yet claimed authorship. My name is on the paper, but not in the electronic sense in arXiv's servers. There is also a solo-author paper that arXiv that I submitted but arXiv does not have me registered as the author.  Are there any reasons to try to fix this? What are the benefits to having a complete authorship record on arXiv's servers?

My colleague has just published a paper on which I am co-author. This is the first paper that has my name on so I am not familiar with the systems yet.   He has received an email from arXiv to confirm his submission and it gave a "paper password". It recommended he forward this to the co-authors so "They may use it to claim ownership."  What does this mean, why would I want to do it and how do I go about it?


I need help in understanding heap and stack overflow, so it would be a lot helpful if I had few examples to understand the concept well

What is a StackOverflowError, what causes it, and how should I deal with them?


I'm relatively new at Python programming.   In C++, there may be multiple classes in a single C++ file. But more often than not, I find myself declaring/implementing only one class in each file. In Java, it is mandatory to have only one public class in each file. When I do C++ or Java programming, I usually make the file name very similar to the class contained in the file. For example, if I implement a "Student" class, then I created "Student.h" and "Student.cc".  In Python, it seems like there is no such restriction, but due to my previous habit, I find myself still creating only one class in each python file, and making the file name very similar to the class name. But I think this might look somewhat absurd.  Suppose that we create a class named FrameProcessor in a file named "frame_processor.py". When we use this class in another python file located in the same directory, we need to do as follows:  import frame_processor def SomeFunction():    processor = frame_processor.FrameProcessor()   I think having both frame_processor and "FramePrcoessor" looks like a duplication. For me, it looks quite redundant, since the file name frame_processor and the class name FrameProcessor are almost the same.  In short, would it be a good habit to have only one class in each python file?

I'm used to the Java model where you can have one public class per file.  Python doesn't have this restriction, and I'm wondering what's the best practice for organizing classes.


I have an iPhone that was synced to an iTunes library. Then I upgraded my Mac, and forgot to backup the iTunes library and transfer it to the new Mac. Ever since, I have been manually managing my music by dragging and dropping it from the filesystem onto iTunes, and not "syncing".  And things have been working fine for the past few years. But now, after yet another Mac upgrade, and upgrading to iTunes 11, I can no longer manually manage my music on my iPhone. When I try to turn on "manually manage music and videos", iTunes says:  The iPhone “kPhone” is synced with another iTunes library on “kart's macbook”. Do you want to erase this iPhone and sync with this iTunes library?  I don't want to erase the whole phone -- apps, app data, app settings, synced data in apps, videos, books, etc. I just want to copy music onto the iPhone. I have already deleted the music that's already on the iPhone. How do I copy music?

I just plugged my iPhone into my new mac (previously it was managed using itunes on a PC)  I just want to delete some songs that are on the iPhone.  It seems I can't press delete on the songs in iTunes when the phone is connected.  When I select Manually manage my songs and videos it prompts "the iphone is synced with another itunes library. Do you want to erase this iPhone and sync with this iTunes library?"  I don't understand because it was manually managed on my PC not synced to a library. Also the prompt isn't very helpful, what does "erase this iPhone" mean? Delete everything? Just music and videos?  If I check "Manually manage my songs and videos" and receive the prompt which says it will "erase this iPhone" what will it actually erase? Is it just the songs and videos?


I have a DEM raster file downloaded from the . The file can be downloaded .  I am trying to create a slope raster in percent with the DEM tool in QGIS. The GDAL command is the following:  gdaldem slope /Users/Downloads/n41w107/imgn41w107_13.img /Users/Downloads/slope.tif -p -s 1.0 -b 1 -of GTiff   The tool runs fine, but the created file slope.tif has strange data. The statistics for the band are the following:  STATISTICS_MAXIMUM=29834248 STATISTICS_MEAN=1845376.751065 STATISTICS_MINIMUM=0 STATISTICS_STDDEV=1658350.0283881   So they are obviously way to big for percent. What am I doing wrong?    Update: I calculated the Slope in degrees and got the following statistics:  STATISTICS_MAXIMUM=89.999809265137 STATISTICS_MEAN=89.583139343302 STATISTICS_MINIMUM=0 STATISTICS_STDDEV=5.9592219763749   A mean of 89 degrees seems really high to me. Is that reasonable?

I'm attempting a simple slope analysis in QGIS2 using the plugin at Raster -> Terrain Analysis -> Slope. The slope output layer has a very strange histogram, basically spikes at 0 and at 89.9098 with one big valley in the middle:    Here's the initial DEM:    And the resulting slope layer (note that Contrast Enhancement is already at 'stretch to minmax'):    The place I got the DEM is the NED. I tried the gridfloat format, and the arcgrid format, and the IMG format. I downloaded from nationalmap and also from atlas.ca.gov - all seem to have the same resulting histogram.  The procedure I used to make the slope layer was Raster -> Terrain Analysis -> Slope, GeoTIFF, Z factor = 1.0 (what does that do anyway?)  Seems like simple pilot error; however: I found  online (for QGIS 1.something) that comes with a sample DEM, and it worked just fine using the same procedure. So, it's not a fundamental QGIS2 bug.  So, it must be slightly more complex pilot error: there must be a conversion step or something I'm missing?


Does anyone know of a listing of all rings (or at least those that are commutative) of a given order?  In particular $p^3$, for a prime $p$.

Like structure theorem for finite abelian groups or modules over PID, is there any structure theorem for finite rings? Thanks.


As , reviewing questions is a thankless job. The OP of that question had a good point. Today, I noticed the Triage feature for the first time. I've probably spent a good 2-3 hours churning through the queue, helping out. It's at about this length of time/moment that I thought "This is monotonous and costly. Am I getting anything in return for this beyond the pride of charity?" I'm not suggesting that reviewing isn't at all rewarding. Anonymous donations are after all a thing. At this point in my day though, I would not continue reviewing without an added incentive. In fact, I'm actually a bit disappointed in the amount of time I've allowed myself to spend sucked into so far today in terms of the cost metric. Where many of us often charge base rates of $100, $200, $300+ for our time, I'm sure many would agree. I was a bit taken back that the aforelinked question had been closed as "Off-topic" - ironic as a Meta question directly related to the review of the validity of questions themselves. Note that: this question is titled "Award" and not "Award rep," though rep points are the primary reward on this site to date. The question is: Are there any conceivable & useful + relatively secure rewards for reviewing questions? Some obvious potential answers come to mind:  A secondary points or ranking system. What benefit it confers is debatable. Monetary or cryptocurrency compensation. Standard rep points + an anti-robot system that's extremely difficult to game. A KYC process for becoming an incentivized reviewer. Hand-pick or rank-threshold users from which review-audit questions must be associated in order to be derived.  The viability of any one solution is not implied. Questions & answers are potentially gambled therefore making reviews gamble removes a potential check on the former. This is simply a means to discuss potential solutions. I don't know what the review-queue to reviewer ratio is at present. If the queue is currently being consumed at a sufficient rate by charity, the stats showing that would be the proper answer. If not, this question seeks to solve it. On the topic of robot-reviews, consider that there are many good engineers & scientists around here who deal with that proposition daily. Good ideas abound.

Formerly List of all badges with full descriptions.  What are badge name's requirements? Why didn't I get badge name ? Which badges can I earn multiple times?    Jump to:                    Note: Some badges are awarded based on score. The term score means the total number of upvotes minus the total number of downvotes.  Any badge with a *** next to it is one of 20 badges that count towards the  displayed on a moderator candidate in an election. The candidate score is a total of 40 points: the first 20 are awarded based on the user's rep divided by 1000 and rounded down; the second 20 represents the total number of unique badges earned of the 20 that count. Note that if the same badge is earned multiple times, it will only count once towards the candidate score.  Any badge with a "(retired)" next to it is no longer awarded, but is retained by users who previously earned them. See  for more info on what it means for a badge to be retired.       Visit the  of the  on any site to see a complete list of badges that you can filter by earned, unearned, or type.


If T(N) = T(sqrt(N)) + 1 and T(1) = 1  then what is the upper bound i.e O(N) for this function?  sqrt(N) => square root of N

This looks like a question asked , but it isn't.  $$T(n)=\begin{cases} T (\sqrt{n}) + 1 \quad & \text{ if } n>1 \\  1 & \text{ if }n=1\end{cases}$$  My professor gave this to me in class yesterday. This is where I'm stuck:   $$T(n) =  T(n^{1/2})+1 =  T(n^{1/4})+2 = T(n^{1/8})+3 = \dots =   T(n^{1/ 2 ^k})+k$$  Now this will continue till  $$n^{1/ 2 ^k}=1$$  How do I proceed ahead? If I take log on both sides, then RHS becomes zero. How do I solve the relation?  I don't want to use the Master theorem, I want to know where and why am I stuck.


This question is here just to avoid you choosing the wrong Ubuntu version number.  So, this is not about:     nor about   nor   nor   nor   nor .   So in the answer below a simple guide as to what Ubuntu version is good for you, independent of future releases!

What different Ubuntu derivatives are there? And what is special with them?


How can I change my Facebook Page's username/link more than one time?

Do I have to re-register a new Facebook account to change my facebook.com/USERNAME?  Or are there any ways to change it?


I am trying to redirect the output of certain program with threads to certain file.  I have tried running command > file 2&>1 but if command has not stopped running, file will still be empty.  Is there any way to asynchronously dump the output to file?  Example python snippet:  import _thread  def run():     raise ValueError('plah')  _thread.start_new_thread(run, ()) while True:     pass   Running python program.py 2> log.txt does not yield an output in log.txt until the program is manually stopped.

How would I get all outputs of systemd managed python2 script instantly into journal, just like it appears in terminal  I'm on centos 7, but seems to be same on arch  according to systemd manual, stdout and stderr should automatically go to journal  systemd config  #DefaultStandardOutput=journal #DefaultStandardError=inherit   Here is my unit /usr/lib/systemd/system/tick.service  [Unit] Description=Tick  [Service] Type=simple ExecStart=/home/stack/tick   script  #!/usr/bin/python import time import sys  print "Tick" sys.stderr.write('First error\n') time.sleep(10) sys.stdout.write("Tick\n") sys.stderr.write('Second error\n') time.sleep(10)   and here is the output from journal, notice the time and order  Oct 30 14:30:41 controller systemd[1]: Starting Tick... Oct 30 14:30:41 controller systemd[1]: Started Tick. Oct 30 14:30:41 controller tick[5020]: First error Oct 30 14:30:51 controller tick[5020]: Second error Oct 30 14:31:01 controller tick[5020]: Tick Oct 30 14:31:01 controller tick[5020]: Tick   With python3 even stderr is delayed until process ends  I tried similar c program, and seems to be same  but this does not seem to affect bash script  #!/bin/bash echo "Tick" echo "First error" 1>&2 sleep 10 echo "Tick" echo "Second error" 1>&2 sleep 10   journal  Oct 30 14:41:36 controller systemd[1]: Starting Tick... Oct 30 14:41:36 controller systemd[1]: Started Tick. Oct 30 14:41:36 controller tick[5084]: Tick Oct 30 14:41:36 controller tick[5084]: First error Oct 30 14:41:46 controller tick[5084]: Tick Oct 30 14:41:46 controller tick[5084]: Second error


In the final Wheel of Time book, "Memory of Light", protagonist Rand Al'Thor      survives the Last Battle by switching bodies with Moridin.   Afterwards, he finds that he cannot channel, yet somehow lights his pipe.     By instinct, he reached for the One Power to light it. He found   nothing. No saidin in the void, nothing. He paused, then smiled and   felt an enormous relief. He could not channel. Just to be certain, he   tentatively reached for the True Power. Nothing there either.      He regarded his pipe, riding up a little incline to the side of Thakan'dar, now covered in plants. No way to light the tabac. He inspected it   for a moment in the darkness, then thought of the pipe being lit. And   it was.   This event is not explained further - it just happens and he thinks of it as "impossible" before smiling and going about his business. It does seem very similar to how things work in Tel'aran'rhiod, though, with thoughts manifesting as reality.  How did he light the pipe without using either saidin or the True Power? Has Brandon Sanderson or anyone else explained this action?

How did Rand al'Thor do what he did at the end of Memory of light?       By instinct he reached for the One Power to light [the pipe]. He found  nothing. No saidin in the void, nothing. He paused, then smiled and  felt an enormous relief. He could not channel. Just to be certain, he  tentatively reached for the True Power. Nothing there either.   ... He inspected it for a moment in the darkness, then thought of the  pipe being lit. And it was.   How was this achieved, and what are the implications?


I got following error when trying to install MySQL workbench

How do I get to the Universe Repository in supported versions of Ubuntu?


How to show $(a_1a_2\ldots a_n)^{\frac{1}{n}}\leq \frac{\sum_{i=1}^{n}a_i}{n}$ with $a_i$ positive. Well, I tried by induction: with $n=2$ then $\sqrt{ab}\leq \frac{a+b}{2}$ is equivalent to say (elevate square in both side) $4ab\leq a^2 +2ab + b^2$ and this is equivalent $0\leq(a-b)^2$ and this is true. I suppose it is true for some $n$. But with $n+1$, I don't know how to do, Please can help me with a hint or other way, thank you so much.

This was a mathematical induction question proposed in a textbook, and I've exhausted multiple approaches (proving RHS - LHS > 0, splitting the fraction, fractional exponents, etc.)     The geometric mean of $n$ positive numbers $a_1, a_2,\ldots,a_n$ is $\sqrt[n]{a_1a_2 \ldots a_n}$ and their arithmetic mean is $\frac{a_1+a_2+\ldots+a_n}{n}$. If $a_1, a_2,\ldots,a_n$ are $n$ positive real numbers, prove by induction that their geometric mean is always smaller than or equal to their arithmetic mean, i.e. $\sqrt[n]{a_1a_2\ldots a_n} \leq \frac{a_1+a_2+\ldots+a_n}{n}$


In HP, do Wizards from different nationalities have different names for spells, and if so do they have to pronounce them as such during the casting?  It seems that more veteran wizards don't seem to need to pronounce many of the spells they are casting, and whilst I am sure this has been explained somewhere, I imagine it has something to do with loading the spell with meaning/empowerment.  However, younger wizards DO seem to need to say the words of the spell they are casting, and if so how is this affected by different languages? Would a mute non-muggle be unable to qualify for wizardry, for example?

The spells that we know about in the Harry Potter world all seem to be either in Latin, derived from Latin, or resembling Latin.  This makes sense for the European World, but there were likely witches and wizards in Africa, Asia, and the Americas.  These cultures would have developed independently, and the magical people in them would likely have still found ways to cast their spells.  Do cultures with languages that did not derive from Latin use the same words and phrases that are related to Latin for their spells?  Or did they have other phrases based on the languages in their cultures?


Is there a Lagrangian reproducing Maxwell's equations without the use of the scalar and vector potential? Obviously $\mathcal{L} = -\frac14F_{\mu \nu}F^{\mu \nu}$ doesn't work since in terms of $E$ and $B$ fields it doesn't contain timederivatives of those and won't reproduce dynamics.  What I'm looking for is a Lagrangian that reproduces Maxwell equations when varied wrt $E$ and $B$ and does not contain any reference to the unphysical $A^\mu$

Is it possible to formulate classical electrodynamics (in the sense of deriving Maxwell's equations) from a least-action principle, without the use of potentials? That is, is there a lagrangian which depends only on the electric and magnetic fields and which will have Maxwell's equations as its Euler-Lagrange equations?


$$\large\lim_{n\to \infty}\large\frac{\sum_{k=1}^n k^p}{n^{p+1}}$$  I'm stuck here because the sum is like this: $1^p+2^p+3^p+4^p+\cdots+n^p$.  Any ideas?

By considering:  $$\lim_{n\to\infty}\frac{\sum_{k=1}^n k^1}{n^{2}} = \frac 1 2$$ $$\lim_{n\to\infty}\frac{\sum_{k=1}^n k^2}{n^{3}} = \frac 1 3$$ $$\lim_{n\to\infty}\frac{\sum_{k=1}^n k^3}{n^{4}} = \frac 1 4$$  Determine if this is true: $$\lim_{n\to\infty}\frac{\sum_{k=1}^n k^m}{n^{m+1}} = \frac 1 {{m+1}}$$  If it is, prove it.  If it is not, evaluate $\lim\limits_{n\to\infty}\frac{\sum_{k=1}^n k^m}{{m+1}}$.


Where can I find themes for Ubuntu 12.04 ?

This might already be answered, but I can't find it.   I am getting a bit bored of the traditional purple feel of unity and I would like something new. Where can I find more Unity themes?  I have already tried synaptic, but could not find anything. I would rather avoid people's personal PPA's.


So, since last restart my Ubuntu won't log in, it just loops.  Here's a video of what happens:   Ive tried to follow a few tutorials and solutions like making a new Xauthority file but so far no luck.  Also, the resolution is weird.  Please help, Thanks.

My Ubuntu is stuck in a login loop when trying to enter my desktop. When I login, the screen gets black and soon after that the login screen comes back.   I've read that the problem might be caused by an error depending on the graphics, here's my graphics card: ATI Radeon 7670M


I'm using alfred so no need in launchpad.  Is it safe to delete launchpad, any applications that depends from it?  How i can remove launchpad? Maybe AppCleaner application can help?  Thanks.

I don't use the launchpad, especially as it has a lot of useless apps in there that you can't delete either. For things like the dock and the dashboard I found guides online on how to remove them, but none for launchpad. Is it possible to remove launchpad completely (on OS X 10.9.4)?


Okay, so, I was reading a book on set theory and I stumbled upon the problem described in the title. The only axioms and axiom schemes that are assumed are the following: Axiom of Existence Axiom of Extensionality Axiom of Comprehension Axiom of Pair Axiom of Union Axiom of Power Set Axiom of Infinity From the theory developed so far I can prove that if A is a set then, for all $n\in\mathbb{N}$, $A^{n}$ (the cartesian product of $n$ copies of $A$) is also a set. I can also prove by induction that, for all $N\in\mathbb{N}$,  $\bigcup_{n=1}^{N}A^{n}$ is also a set. But I can't seem to be able to show that the countable union is a set. Well, I can, but it feels like I'm cheating, so to speak. My idea goes as follows. The book already outlines a proof that $A^{B}$ (the collection of functions from a set $B$ into a set $A$) is a set. I will assume this fact. In particular, we have that $A^{\mathbb{N}}$ is a set. Now we can easily define functions $f_{n}$ from $A^{n}$ into $A^{\mathbb{N}}$ in such a way that $im(f_{i})\cap im(f_{j})=\emptyset$, whenever $i\neq j$. Informally, the idea is taking an element of $A^{n}$ and adding a trail of $n$ at the end. Now, this is where I feel the cheat is. We can "identify" (I choose to use the quotation marks because the book hasn't formally defined this idea, even though I know this kind of trick is used all the time in other areas) $A^{n}$ with its image. So I kind of proved that all of the $A^{n}$ can be realized within $A^{\mathbb{N}}$ (with no overlapping), so their union also can be realized as a subset of $A^{\mathbb{N}}$. This in turn "shows" (with big quotation marks) that the countable union of the $A^{n}$ is a set, as intended. However, I feel that this isn't entirely correct from the point of view of axiomatic set theory, since at no point in the book so far it was shown that if a set $X$ can be realized as a subset $Y$ of another set $Z$, then this implies that $X$ must be a set. No theorems about cardinality have been proven up to this point in the book, either. I feel like the correct way to prove something is a set is either explicitly constructing it from the axioms, or showing that it is a subset of another set, which isn't the same as showing that it can be identified with a subset of another set. This might seem excessively nitpicky, but that's precisely the point. I'm interested in proving this without making any assumptions that don't follow from the axioms listed above. Anyway, I would really appreciate your input. If this argument is correct (and I think it's not), I would really like to know how to justify it. If it's not, how should I go about proving this? I think a hint or two should be enough to get me on the right track.

I need to prove that the set $\{A^n : n \in \mathbb{N} \}$ using the ZFC axioms (without Replacement).  My (rough) plan would be to construct some set containing "more" sets than necessary, then use the comprehension axiom to remove the undesirable sets. Something like: for some $Y$, $\{ X \in Y : \exists n \in \mathbb{N}, X = A^n\}$.  I know how to prove that any one of these sets (e.g., $A^2$), exists, but I have no idea how to prove that the set containing all of these powers exists.


Is there any way to change one's nationality in a PayPal account without having to open a new one?

I just moved from Canada to US and want to add my USA address and credit card with US billing address to PayPal, but not able to do this. I read this  from 2011, and it looks like I need to open new PayPal account.  Is it only way to do this?   I prefer to use the same account with Canadian and US credits card on it.


How to install skype in ubuntu 16.04? Please provide step by step process for installation.

I want to install Skype, but I can't locate it in Software Center or by using Synaptic Package Manager. Can anyone help me?


Take a look at this cooling fan from a Dell D630:  Another cooling fan, from an XP desktop:  Notice that only the desktop's cooling fan has the 4th wire. Why is that so?

What is the difference between 3-Wire and 4-Wire CPU cooling fans?  Of course, the obvious answer is “1 Wire!”  :-)


What I would love from this question is advice please on   best way to install python 3.7 as the default python best way to install packages   I'm very new to the command line. I'm in the middle of a Data Science boot camp and trying out some things on Ubuntu, however, many of the commands we're learning don't seem to be installed (including the installer...).  e.g. python   iboopedu@CODE1026:/mnt/c/Users/shane$ python  Command 'python' not found, but can be installed with:  sudo apt install python3 sudo apt install python sudo apt install python-minimal  You also have python3 installed, you can run 'python3' instead.   e.g. pip  iboopedu@CODE1026:/mnt/c/Users/shane$ pip install python  Command 'pip' not found, but can be installed with:  sudo apt install python-pip  iboopedu@CODE1026:/mnt/c/Users/shane$ sudo apt install python-pip [sudo] password for iboopedu: Sorry, try again. [sudo] password for iboopedu: Reading package lists... Done Building dependency tree Reading state information... Done E: Unable to locate package python-pip   e.g. virtualenv  iboopedu@CODE1026:/mnt/c/Users/shane$ virtualenv test  Command 'virtualenv' not found, but can be installed with:  sudo apt install virtualenv  iboopedu@CODE1026:/mnt/c/Users/shane$ sudo apt install virtualenv Reading package lists... Done Building dependency tree Reading state information... Done E: Unable to locate package virtualenv   Troubleshooting  I also use a Mac, and on Terminal and all of the above commands work fine without any special set-up or install, running python from Anaconda.  Given this, I've attempted to replicate running python from Anaconda on Ubuntu.   I've tried the following without success:   Changed PATH manually to include Anaconda's python.exe   iboopedu@CODE1026:/mnt/c/Users/shane/Documents$ echo $PATH /mnt/c/Users/shane:/mnt/c/Users/shane/Anaconda3/Library/bin:/mnt/c/Users/shane/Anaconda3/Scripts:/mnt/c/Users/shane/Anaconda3:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/mnt/c/Program Files/WindowsApps/CanonicalGroupLimited.UbuntuonWindows_1804.2018.817.0_x64__79rhkp1fndgsc:/mnt/c/Windows/System32:/mnt/c/Windows:/mnt/c/Windows/System32/wbem:/mnt/c/Windows/System32/WindowsPowerShell/v1.0:/mnt/c/Program Files (x86)/Windows Live/Shared:/mnt/c/Windows/System32:/mnt/c/Windows:/mnt/c/Windows/System32/wbem:/mnt/c/Windows/System32/WindowsPowerShell/v1.0:/mnt/c/Program Files (x86)/GNU/GnuPG/pub:/mnt/c/Windows/System32:/mnt/c/Windows:/mnt/c/Windows/System32/wbem:/mnt/c/Windows/System32/WindowsPowerShell/v1.0:/mnt/c/Windows/System32/OpenSSH:/mnt/c/Program Files (x86)/NVIDIA Corporation/PhysX/Common:/mnt/c/Program Files/NVIDIA Corporation/NVIDIA NvDLISR:/mnt/c/Users/shane/AppData/Local/Microsoft/WindowsApps:/mnt/c/Users/shane/AppData/Local/Programs/Microsoft VS Code/bin:/snap/bin    Reinstalled Anaconda with install option to auto add Anaconda to PATH   iboopedu@CODE1026:/mnt/c/Users/shane$ echo $PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/mnt/c/Program Files/WindowsApps/CanonicalGroupLimited.UbuntuonWindows_1804.2018.817.0_x64__79rhkp1fndgsc:/mnt/c/Windows/System32:/mnt/c/Windows:/mnt/c/Windows/System32/wbem:/mnt/c/Windows/System32/WindowsPowerShell/v1.0:/mnt/c/Program Files (x86)/Windows Live/Shared:/mnt/c/Windows/System32:/mnt/c/Windows:/mnt/c/Windows/System32/wbem:/mnt/c/Windows/System32/WindowsPowerShell/v1.0:/mnt/c/Program Files (x86)/GNU/GnuPG/pub:/mnt/c/Windows/System32:/mnt/c/Windows:/mnt/c/Windows/System32/wbem:/mnt/c/Windows/System32/WindowsPowerShell/v1.0:/mnt/c/Windows/System32/OpenSSH:/mnt/c/Program Files (x86)/NVIDIA Corporation/PhysX/Common:/mnt/c/Program Files/NVIDIA Corporation/NVIDIA NvDLISR:/mnt/c/Users/shane/Anaconda3:/mnt/c/Users/shane/Anaconda3/Library/mingw-w64/bin:/mnt/c/Users/shane/Anaconda3/Library/bin:/mnt/c/Users/shane/Anaconda3/Scripts:/mnt/c/Users/shane/AppData/Local/Microsoft/WindowsApps:/mnt/c/Users/shane/AppData/Local/Programs/Microsoft VS Code/bin:/snap/bin   That's where I am, hopefully someone can help! Thanks in advance.

I have python3 installed in Ubuntu 18.04 and I want to use different modules of python. Can anyone tell me how to install them?


please tell me how to print out result from Array static method  public static void main(String[] args) {         System.out.println(add(1, 2));         String a = "Learn Java";         System.out.println(test(a));     }     public static int add(int a, int b){        return a + b;     }     public static String[] test(String a){         return a.split("[ ]");     }   if I print out "add", the result : 3 but when I print out "test", the result show hex number.

In Java, arrays don't override toString(), so if you try to print one directly, you get the className + '@' + the hex of the  of the array, as defined by Object.toString():  int[] intArray = new int[] {1, 2, 3, 4, 5}; System.out.println(intArray);     // prints something like '[I@3343c8b3'   But usually, we'd actually want something more like [1, 2, 3, 4, 5]. What's the simplest way of doing that? Here are some example inputs and outputs:  // Array of primitives: int[] intArray = new int[] {1, 2, 3, 4, 5}; //output: [1, 2, 3, 4, 5]  // Array of object references: String[] strArray = new String[] {"John", "Mary", "Bob"}; //output: [John, Mary, Bob]


I have an Asus R503U laptop with AMD C-60 1.0 GHz processor with 4 Gb of RAM. It is a 64-bit system. I also have a lower end Radeon Graphics card. Currently I am running Windows 10. I'm looking for something that would be easier on the processor and light on the ram to be able to play games and videos a little better.

For a given hardware configuration, how do I find out if Ubuntu will run on it? What considerations should I take into account when choosing an Ubuntu version and  such as:    with a lighter desktop than the usual Gnome and Unity  with the even lighter LXDE desktop   Obviously Ubuntu does not run on some processor architectures. So how do I go about choosing the right version and derivate. How can I find out the minmal system requirements?


This topic similar with this one  But I perfrom exponential smoothing model in R.  df=structure(list(date = structure(1:12, .Label = c("01.01.2017",  "01.02.2017", "01.03.2017", "01.04.2017", "01.05.2017", "01.06.2017",  "01.07.2017", "01.08.2017", "01.09.2017", "01.10.2017", "01.11.2017",  "01.12.2017"), class = "factor"), value = c(200L, 100L, 460L,  300L, 280L, 280L, 140L, 180L, 80L, 80L, 180L, 60L), common = structure(c(1L,  1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = "158150- 01195т", class = "factor")), .Names = c("date",  "value", "common"), class = "data.frame", row.names = c(NA, -12L ))   i perform forecast for each groups separately) using ets function from forecast package (common is grouping variable)  here forecast for initial dataset   it is wrong result, but the main is that forecast on 1 year age ahead has static values(like historical mean)   How can i understand why forecast show same value in exponential smoothing model. Is it possible to fix it?  I can provide my R code, if it is needed.

I am trying to forecast time series data for next $n$ time periods and I am using various forecasting techniques like simple moving average, exponential smoothing (Single,double,triple) and auto.arima().  I am getting equal forecasting values for simple moving average and single exponential smoothing and at times, even auto.arima() function in R is giving me the same forecast values.  Here is the code that I am trying to use  mod_mva <- SMA(data.train,n=2) forecast_mva <-forecast(mod_mva,ts_freq)   Here is the output:


I would like to pin a file's shortcut to the dock in the Ubuntu 18.04 GNOME desktop so that the file opens directly when I click it, for example a spreadsheet file that opens with LibreOffice Calc. Is this possible?

I miss those pins I make in Windows.     How can I do the same in Ubuntu 17.10 with GNOME 3?


In Bayes Statistics, does the accepted sample based on the acceptance-rejection algorithm has the same distribution as X~$f(x)$? Intuitionally it does, but how to prove it under the discrete and continuous cases respectively?

I did not fully understand the proof of the acceptance probability.   The acceptance-rejection algorithm is described as follows:   suppose you have RVs $X$ and $Y$ with densities $f$ and $g$, respectively, and there exists a constant $c$ such that $\frac{f(t)}{g(t)} \leq c$ for all $t$ such that $f(t) > 0$, then    generate random $y$ from distribution with density $g$ generate random $u$ from $\text{Uniform}(0, 1)$ if $u < \frac{f(y)}{cg(y)}$ accept $y$ and deliver $x = y$, otherwise repeat    In Rizzo's book 'Statistical Computing with R' (p56) he writes  $P(\text{accept}|Y)=P(U<\frac{f(Y)}{cg(Y)}|Y)=\frac{f(Y)}{cg(Y)}$  and so  $\sum_y{P(\text{accept}|y)P(Y=y)}=\sum_y{\frac{f(y)}{cg(y)}g(y)}=\frac{1}{c}$  This still makes sense to me, but what about the continuous version of this proof, which is as follows:  $ \begin{aligned} P(A) =& \int_{-\infty}^{\infty}dy\int_0^{\frac{f(y)}{cg(y)}}g(y)du \\ =& \int_{-\infty}^{\infty}\frac{1}{c}f(y)dy \\ =& \frac{1}{c}. \end{aligned} $  Could someone explain to me specifically how you get to this double integral?


How can I prove that $4^n-3n-1$ is divisible by $9$? I tried dividing the expression by $9$ and seeing if the terms cancelled in any predictable way but I still cannot prove it. Maybe there is a clever solution but so far I have been unable to spot it.

My textbook provided the following proof:        Base case: When $n=0, 9^n-8n-1=0=64\cdot0$, so $64\mid\left(9^n-8n-1\right)$.      Induction step: Suppose that $n\in\mathbb N$ and $64\mid\left(9^n-8n-1\right)$. Then there is some integer $k$ such that $9^n-8n-1=0=64k$. Therefore:      $$\begin{align} 9^{n+1}-8(n+1)-1&=9^{n+1}-8n-9\\ &=9^{n+1}-72n-9+64n\\ &=9\left(9^n-8n-1\right)+64n\\ &=9(64k)+64n\\ &=64(9k+n) \end{align}$$      so $64\mid\left(9^{n+1}-8(n+1)-1\right)$.      What I don't understand is how the equation goes from   $$= 9^{n+1} - 8n - 9$$  to   $$= 9^{n+1} - 72n - 9 + 64n$$


I wrote two functions push and pull to copy files to and from a directory ($FILE_EXCHANGE_DIR). I want bash to autocomplete names from that directory when I use the pull function. I want the autocompletion to only take names from the said directory. In the current form, my autocompletion also finds names of the files in the current directory, regardless of whether there was a match in the source dir ($FILE_EXCHANGE_DIR) or not.  Here are two versions of the function I passed to complete. Neither of them worked.  _pull () {     local cmd="${1##*/}";     local word=${COMP_WORDS[COMP_CWORD]};     local line=${COMP_LINE};     filelist=( $(ls ${FILE_EXCHANGE_DIR} ) )      local TEMP_COMPREPLY=( $(compgen -W "${filelist[@]}" -- ${word} ) )      COMPREPLY=( "${TEMP_COMPREPLY[@]}" )     return 0; }  _pull ()  {     local word=${COMP_WORDS[COMP_CWORD]};     local line=${COMP_LINE};     local pat="$FILE_EXCHANGE_DIR/*"      COMPREPLY=($(compgen -f -G "$pat" -- "$FILE_EXCHANGE_DIR/${word}"));      i=0     for item in "${COMPREPLY[@]}"; do         COMPREPLY[$i]="${item##*/}"         i+=1     done;     return 0; }   In the end, I do  complete -f -F _pull pull   Is there a good way of completing names only from one directory (that is not the current one) and not from current? Even in the case when there was no match in the source (which should default to readline default completion?

This question is quite similar to , but I can't understand the solution. I also know , but still I am unable to understand what I am doing wrong.  I am trying to autocomplete the list of directories that are placed in /something/:  $ ls /something/  One    Other    Three   in a way that this will happen:  $ hi [TAB]  One Other Three $ hi O[TAB]  One Other   Only when the first word is hi and not only inside /something/.  This is what I am doing in .profile:  _codeComplete() {     local cur=${COMP_WORDS[COMP_CWORD]}     COMPREPLY=( $(compgen `ls /something/` -- $cur) )  } complete -F _codeComplete "hi "


I have an element with the following style:  p {   color: 'red'; }   When I'm trying to get the element color by running the following code:    const styles = window.getComputedStyle(pElem);   const value = styles.getPropertyValue('color');   I'm getting the color in RGB format. How I can get the real value - 'red'?  I need this functionality for testing purposes, for example:  expect(p).toHaveStyle({color: 'red'});

I would like to return a string with all of the contents of a CSS rule, like the format you'd see in an inline style. I'd like to be able to do this without knowing what is contained in a particular rule, so I can't just pull them out by style name (like .style.width etc.)   The CSS:  .test {     width:80px;     height:50px;     background-color:#808080; }   The code so far:  function getStyle(className) {     var classes = document.styleSheets[0].rules || document.styleSheets[0].cssRules     for(var x=0;x<classes.length;x++) {         if(classes[x].selectorText==className) {             //this is where I can collect the style information, but how?         }     } } getStyle('.test')


Christoffel symbols explain the gravity we observe in our daily lives. Say I have a region of spacetime with high , so general relativity isn't a good description of the region. In that region, be it a room or a Solar system depending on what would make for a good thought experiment, what would be empirically different from GR's predictions? We'll focus on classical effects, viz. something like  or whatever else would be a "mainstream" theory with torsion.

In general relativity, we assume that the connection is torsion-free. In some alternate theories, like Einstein-Cartan theory, we consider connections with torsion.   According to , torsion can be measured through the precession of spins, but this requires understanding spinors in GR. Is there a way to directly measure torsion without using spin, ideally through a simple mechanical system? (I don't care if this is an impractical experimental test, I just want intuition for what the torsion tensor means physically.)


Consider the number $b_h$ of binary trees of height $h$, where height is being measured by the number of levels. An empty tree has height $0$, a single node binary tree has height $1$, and there are three trees of height $2$. Find a recursive algebraic equation for a sequence $b$, and prove for all natural numbers $h$ that $b_{h}$ is the number of binary trees of height $h$.   Assuming $b_{1} = 1$ binary Tree.  Then $b_{2} =  3$ binary Trees.  The difference is increasing by $+1$, $+2$, ..., $+(h-1)$.  How can we get the recursive algebraic equation for this? I'm really confused.

I'm trying to figure out a recursive formula for the number of possible distinct binary trees at any depth d. I haven't been able to find any sort of sources on this.  basically, at depth 0, the only binary tree is the empty one so 0, 1  then at depth 1 the only possibility is a single node so 1, 1  at depth = 2 there are 3 possibilities, and at depth 3 I counted 21 possibilities.  I haven't been able to figure out some recursive reasoning for what 4 could be and so on. The only thing I have in place is that there will always be 1 for the full tree.


Now I got a dictionary like this  Dictionary dict = new Hashtable(); dict.put("shipno", item.getShipNumber()); dict.put("addr", item.getFinalAddr()); dict.put("receiver", item.getReceiverName()); dict.put("phone", item.getReceiverPhone());   and I'm going to pass this dictionary to funcion Test() as a parameter, what should I put in the '()'  public static int Test(Dictionary)   Is this correct? Thanks!

I have seen this mentioned a few times and I am not clear on what it means. When and why would you do this?   I know what interfaces do, but the fact I am not clear on this makes me think I am missing out on using them correctly.   Is it just so if you were to do:  IInterface classRef = new ObjectWhatever()   You could use any class that implements IInterface? When would you need to do that? The only thing I can think of is if you have a method and you are unsure of what object will be passed except for it implementing IInterface. I cannot think how often you would need to do that.   Also, how could you write a method that takes in an object that implements an interface? Is that possible?


I am taking Real Analysis in the Fall and the Professor recommended Spivak's Calculus to prepare for the course. Unfortunately, someone was faster than me and already borrowed the book from the library and I don't want to buy it. Does anyone have a similar book they recommend, covering advanced calculus as a preparation for real analysis? I already have Abbott's "Understanding Analysis" (he's a professor here, really nice guy, plays electric guitar in the faculty band).

Does anyone have a recommendation for a book to use for the self study of real analysis? Several years ago when I completed about half a semester of Real Analysis I, the instructor used "Introduction to Analysis" by Gaughan.   While it's a good book, I'm not sure it's suited for self study by itself.  I know it's a rigorous subject, but I'd like to try and find something that "dumbs down" the material a bit, then between the two books I might be able to make some headway.


I've just bought a game (Machinarium) which does not come with a deb file neither is it a ./configure, make etc type of application. I can just run it. Where is the best place to put it so i can create a launcher and keep it out of my home directory?   i.e. I'm basically asking where are applications are installed and should i put this game there.  Thanks!

Occasionally I install applications manually, rather than using apt or another package manager.   What location (/usr/, /usr/local/, /opt/, /home/, etc.) is suggested by "best practices" for the installation of user applications?


Is there an easy way to run a MySQL query from the linux command line and output the results in csv format?  Here's what I'm doing now:  mysql -u uid -ppwd -D dbname << EOQ | sed -e 's/        /,/g' | tee list.csv select id, concat("\"",name,"\"") as name from students EOQ   It gets messy when there are a lot of columns that need to be surrounded by quotes, or if there are quotes in the results that need to be escaped.

Is there an easy way to run a MySQL query from the Linux command line and output the results in  format?  Here's what I'm doing now:  mysql -u uid -ppwd -D dbname << EOQ | sed -e 's/        /,/g' | tee list.csv select id, concat("\"",name,"\"") as name from students EOQ   It gets messy when there are a lot of columns that need to be surrounded by quotes, or if there are quotes in the results that need to be escaped.


Find the coefficient of $z$ in the Laureant Series expansion of $\frac{e^z}{z-1}$ in $\{|z|>1\}$.    Ok, so for $|z|>1 \iff |\frac{1}{z}|<1$ I can write  $\frac{1}{z-1}=\frac{1}{z}\cdot \frac{1}{1-\frac{1}{z}}=\frac{1}{z}\sum_{n=0}^{\infty}(\frac{1}{z})^n=\frac{1}{z}\sum_{n<0}z^n$  Which is the Laureant Series for $\frac{1}{z-1}$.  But I don't know what to do with the $e^z$ multiplying. How should I proceed?

I've found this duplicate from '15: , but I think it's wrong, since it looks for the Laurent expansion in ${|z-1|>1}$.   After developing it by myself, I've reached the following:  $$f(z)=\frac{e^z}{z-1}=\frac{1}{z-1}\cdot e^z$$  Then, $e^z=\sum_{n\geq 0} \frac{z^n}{n!}$ and $$\frac{1}{z-1}=\sum_{n \geq 0} \frac{1}{z^{n+1}}$$.  Here I thought of using the Cauchy Product, but I end up with  $$f(z)=\sum_{n \geq 0} \sum_{k=0}^n \frac{z^{2k-n-1}}{k!}$$ (How can I make this font bigger? The exponent is too small. Sorry about that. The exponent would be $2k-n-1$).  So I have to sum whenever $2k-n-1 = 1$  If I'm not getting it wrong, this means that I have to calculate $$\sum_{n \geq 0} \frac{1}{(1+2n)!}$$ (I'm not sure how to show it better, but I've put the first 3 terms and were $\frac{1}{1!}, \frac{1}{3!}$ and $\frac{1}{5!}$. I'm not sure how to calculate that. The nearest thing I thought was that $$\sum_{n \geq 0} \frac{1}{n!}=e $$. Maybe what I found before could be considered as an answer, but I think I can go one step further.  Thanks


I have long pieces of \LaTeX code given to me which look lie the following.  \begin{flushleft} \small \begin{minipage}{\linewidth}\label{scrap1}\raggedright\small \NWtarget{nuweb13}{} \verb@"../main.py"@\nobreak\ {\footnotesize {13}}$\equiv$ \vspace{-1ex} \begin{list}{}{} \item \mbox{}\verb@@\\ \mbox{}\verb@import sys@\\ \mbox{}\verb@sys.path.append('src/lib')@\\ \mbox{}\verb@@\\ \mbox{}\verb@import problem_foo\\ \mbox{}\verb@import problem_bar\\ \mbox{}\verb@   @\\ \mbox{}\verb@if __name__=="__main__":@\\ \mbox{}\verb@     if (len(sys.argv)==1):@\\ \mbox{}\verb@          print "Specify the problem"@\\ \mbox{}\verb@          sys.exit()@\\ \mbox{}\verb@@\\ \mbox{}\verb@     elif sys.argv[1] == "--problem-foo":@\\ \mbox{}\verb@          foo.run_handler()@\\ \mbox{}\verb@@\\ \mbox{}\verb@     elif sys.argv[1] == "--problem-bar":@\\ \mbox{}\verb@          bar.run_handler()@\\ \mbox{}\verb@@\\ \mbox{}\verb@@\\ \mbox{}\verb@     else:@\\ \mbox{}\verb@          print "Option not recognized"@\\ \mbox{}\verb@          sys.exit()@\\ \mbox{}\verb@@{\NWsep} \end{list} \vspace{-1.5ex} \footnotesize \begin{list}{}{\setlength{\itemsep}{-\parsep}\setlength{\itemindent}{-\leftmargin}}   I do not like the default font of the verbatim font of \verb that is being  generated in my document. How do I tell \LaTeX to change the verbatim font to  ?   Note: I know, I can probbaly generate better looking output using listings environment for source code, but I am not allowed to edit the code-chunks  I have been given. I just need a way to change the font of \verb to something nicer like inconsolata.

I am new here and the following code is what I am testing. Is it possible to change the typeface of the words from a .txt file? Thank you for any kind help!  \documentclass[a4paper]{article} \usepackage{titling} \newcommand{\subtitle}[1]{%   \posttitle{%     \par\end{center}     \vskip5em     \begin{center}\LARGE#1\end{center}     \vskip5em}% }  \usepackage{palatino} \usepackage[utf8x]{inputenc} \usepackage[top=1in,bottom=1in,left=1in,right=1in]{geometry} \usepackage{indentfirst} \usepackage{lipsum} \usepackage{verbatim} \usepackage{graphicx} \usepackage{booktabs,multirow}  \usepackage{amsmath,amssymb} \usepackage{xcolor} \usepackage{cite}  \begin{document}  \section{Test section} \subsection{Test section} \subsubsection{Test section} \paragraph{Test section} \setlength{\parindent}{0pt}This document is for testing. \Large \verbatiminput{verb.txt}  \end{document}


I have this code:  lst = [] given = [1, 2, 3, 4, 5] result = []  for item in given:     lst.append(item)     print(lst)     result.append(lst)  print(result)   My expected result is [[1], [1, 2], [1, 2, 3], ...], but displayed result is [[1, 2, 3, 4, 5], ...] with 12345 repeated 5 times. What is wrong?  lst printed is as expected, which is [1] for the first loop, [1, 2] for the second loop, and so on.

I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?


At the end of Avengers: Infinity War Thanos snapped his fingers and that erased half of the life in the universe etc. But to my understanding there is no rule book with the gauntlet. He snapped his fingers because that's how he decided to channel his intentions, he mentioned at one point that with all 6 stones he could simply snap his fingers and half would cease to exist (paraphrased badly).  So why did both the Hulk and Iron Man need to do the same in Avengers: Endgame?  Almost as if snapping fingers was the only way to achieve this particular task.

In Avengers: Endgame, is the snap simply dramatic, or does the wielder of the Gauntlet needs to follow this ritual to actually activate it?


My aim here is to reinstall Windows 8 Pro either by resetting or reinstalling from physical media, however I run into problems whichever option I want to use.  Resetting Windows 8 from PC Settings  Everytime I try this I get a message stating, "There was a problem while resetting your pc". This happens if I try it from PC settings, boot options and from a recovery disk. When booting back into Windows I get a window that apparently checks for solutions but nothing happens.  Reinstalling Windows from a media  I upgraded my Windows 7 to Windows 8 Pro using the Windows 8 Upgrade Assistant. I never got an ISO or disk. I have tried downloading an ISO from here: , however when I type my serial number in all I get is a message stating, "The product key you entered is an upgrade key and can't be used to install Windows 8".  Redownload via Windows 8 Upgrade Assistant  This just tells me there is nothing to download in my area / country.  So as you can see, I am in quite a situation. Thanks.

I obtained a licence key for Windows 8 through DreamSpark. Is there a way to download a Windows 8 ISO image like you could for Windows 7? I am on a non-Windows machine, so I cannot use the Secure Download Manager to download Windows 8 directly using DreamSpark.


Skimming through this forum as well as the current documentation of biblatex, I did not find a functionality to achieve this. First, consider this MWE, inspired by :  \documentclass{article}  \usepackage{biblatex}  \usepackage{filecontents}  \begin{filecontents}{\jobname.bib} @misc{FirstEntry,   author = {Author, A. and Donald Duck and Winston Churchill},   year = {2010},   title = {Some Title}, } @misc{SecondEntry,   author = {Buthor, B.},   year = {2020},   title = {Another Title}, } \end{filecontents}  \addbibresource{\jobname.bib}  \nocite{*}  \begin{document}  \textcite{FirstEntry} \textbf{shows} us nothing at all.  \textcite{SecondEntry} shows us a lot.  \printbibliography  \end{document}   yielding    From the biblatex doc, we see that textcite is provided as \textcite[<prenote>][<postnote>]{<key>}, working wonderfully. Now, this is a very minute and niche thing to ask, but is there a function like  \textcite[<prenote>][<postnote>][<base verb>]{<key>}   essentially expanding the command by another optional argument that takes in the base form of a verb, and prints, e.g., do if the textcite and its surrounding settings happen to print a list of authors, like for FirstEntry in my first example, and does if it so happens to print a single author?  It is easy to do this manually. However, it is sometimes not obvious, especially if working with external library software like Zotero, if a bib-entry has just one or multiple authors. This has happenend to me many times now, and if at some point one overlooks the tiny missing (or superfluous) s at the verb's end, it can get embarrasing.  We could then use  \textcite[][][show]{FirstEntry} us nothing at all.  \textcite[][][show]{SecondEntry} us a lot.   and never have to worry again, since it would do nothing to the base verb in the first sentence, and automatically append the s in the second one.  If the authors of the bib entry change later, after the respective passage has long been written, we would not have to worry about that either.  This is also thinkable for other languages.

In my document, I will write something like this (using natbib, but that shouldn't matter too much):  \citet{reference} show that .....   which would render as     Jones et al (1990) show that....   (\citet in \natbib creates an 'author-list (year)' reference style)  Of course if {reference} was a single individual, I should have written  \cite{reference} shows that ....   rendering as     Jones (1990) shows that....   Since I'm lazy and can't take the extra 5 seconds to search the reference to see if it's a single author or not, is there conceivably an automated way to do pluralization ? Or some relatively simple macro that would look like   \IfRefIsPlural{reference}{show}{shows}


Compound microscope is used to see magnified image of tiny objects. Whereas telescope is used to see distant objects' magnified image. I wonder can we use telescope to see small objects placed close to objective lens? And can Compound microscope be used to see celestial objects? They both have two convex lenses the only difference is the focal length and diameter of lenses. So what will be the problems in interchanging their uses?

In compound microscope, we take such an objective lens which has small focal length. While in astronomical telescope, we take such an objective lens which has large focal length.   Why don't we use same objective lens in both? The function of both the devices is to enlarge an object at infinity.


What will happen in random forest if one of the independent variable has no change in value (have same answer) for all the samples?

Is it reasonable to run a random forest model with an independent variables that has almost little or no variations. How they impact the model and whats their role in predicting the dependent?from technical point of view I believe they will not be used in building the tress and will have no role in predicting the DV


I am travelling from mumbai to houston via manchester so uk visa is required if the terminal is same?

Is there a website or some other way to find out if I need a transit visa for a short stop in the UK on my way somewhere else? Ideally this should give me the answer for all nationalities, and take into account any other visas I may have.


I need to do something like that:  a = input('Import the package: ') import a   Problem: a is a string. I do not know how to do it. The best idea I have is to do:  a = input('Import the package: ') if a == 'numpy':     import numpy   But if I need to import many packages, this code can be difficult to read. a = 'numpy' is an example. I need this because I am writing a program that needs to import different scripts in different situations.

I'm writing a Python application that takes as a command as an argument, for example:  $ python myapp.py command1   I want the application to be extensible, that is, to be able to add new modules that implement new commands without having to change the main application source. The tree looks something like:  myapp/     __init__.py     commands/         __init__.py         command1.py         command2.py     foo.py     bar.py   So I want the application to find the available command modules at runtime and execute the appropriate one.  Python defines an __import__ function, which takes a string for a module name:     __import__(name, globals=None, locals=None, fromlist=(), level=0)      The function imports the module name, potentially using the given globals and locals to determine how to interpret the name in a package context. The fromlist gives the names of objects or submodules that should be imported from the module given by name.       Source:    So currently I have something like:  command = sys.argv[1] try:     command_module = __import__("myapp.commands.%s" % command, fromlist=["myapp.commands"]) except ImportError:     # Display error message  command_module.run()   This works just fine, I'm just wondering if there is possibly a more idiomatic way to accomplish what we are doing with this code.  Note that I specifically don't want to get in to using eggs or extension points. This is not an open-source project and I don't expect there to be "plugins". The point is to simplify the main application code and remove the need to modify it each time a new command module is added.


How do I delete a file or folder in Python?

I am getting an 'access is denied' error when I attempt to delete a folder that is not empty. I used the following command in my attempt: os.remove("/folder_name").   What is the most effective way of removing/deleting a folder/directory that is not empty?


Let's be sequence $ (u_n) $  is defined by $u_1=1$, $u_{n+1} =2 u_n+\sqrt{3 u_n^2+6}, \quad \forall n \geq 1.$ Prove that all its members are positive integers.   I tried by using matrix.      Put  $ v_n = \sqrt{3 u_n^2+6} $, then $ v_n^2 - 3u_n^2 = 6 $ and     $$ u_{n+1}=2u_n + v_n, \quad \forall n \geq 1. $$     We have \begin{align*} v_{n+1}^2 &= 3u_{n+1}^2 + 6\\ &= 3(2u_n + v_n)^2 +v_n^2 - 3u_n^2\\ &= 9u_n^2 + 12 u_n v_n + 4v_n^2\\ &= (3u_n + 2 v_n)^2\\ \end{align*} Then, $ v_{n+1} = 3u_n + 2 v_n. $ We have $$ \left( \begin{array}{c} u_1  \\ v_1 \\ \end{array}\right)  = \left( \begin{array}{c} 1  \\ 3 \\ \end{array}\right), \quad \left( \begin{array}{c} u_{n+1}  \\ v_{n+1} \\ \end{array}\right)  = \left( \begin{array}{cc} 2& 1  \\ 3 &2 \\ \end{array}\right)\left( \begin{array}{c} u_n  \\ v_n \\ \end{array}\right)$$  Thus all the numbers $u_ n$ and $v_ n , n ≥ 2,$ are positive integers.  How can I solve this prolbem without using matrix?

I am preparing for Putnam and working through practice-like questions and I am boggled. I've got the sequence defined by $a_1 = 1$ and $a_{n+1} = 2a_n+\sqrt{3a_n^2-2}$ for any $n\in\mathbb{N}$ and I'm trying to show that every term is a positive integer. I am getting as far as  $a_{n+1}^2 -4a_{n+1}a_n + a_n^2 = -2$ but I can't figure out how to use the recursive relationship to show that all terms are integers. I've tried expanding the sequence in terms of $a_n$ or $a_{n+2}$ but it doesn't seem to get me far. Any hints or help would be greatly appreciated.


In S04E06, it is stated several times that Tywin's family-line will end if Tyrion dies or goes to the Night's Watch, and Jaime doesn't get married - which means none of them would have children.  Now I wonder, there are still Tommen and Myrcella who are Cersei's children and thus continue Tywin's family line even if the children are considered to be Robert's children.   So what is the problem about?

According to the family tree in A World of Ice and Fire Ned Stark's children are in fact the only surviving Starks. And as of S06E09;      Bran is the only legitimate, male Stark.   In the Season Six Finale it is revealed that;      Jon is in fact the Son of Lyanna Stark and most likely, Rhaegar Targaryen.   This means that if Jon was legitimised and there was record of his birth in the Citadel;      He would become a Targaryen.   So I guess my big question is: Can Bran father children? I find it to be quite an important issue considering House Stark's long term survival depends on it.  In season 4 (I can't remember which episode) Locke Bolton gives Bran a cut on the leg to confirm his identity. Bran reacts only with fear and not pain, indicating that he has no feeling below his waist.  Does this mean that he wouldn't be able to...get it up? And if so, why hasn't the show addressed House Stark's impending doom?


I want to use the value of \columnsep but I can not find what was the default value.

I wanted to know if someone could point me to a reference where I could learn more about the \the command. Searching for "the" has been, without surprise, entirely unproductive. Even consulting "comprehensive" LaTeX command/macro lists has been unfruitful.   is the only treatment of the subject that I could find, but it was not very informative.


As the title says, the built-in card reader in my MacBook Pro doesn't work. It simply doesn't do anything when I instert an SD card. I'm using Mac OS X 10.6.8.  I guess one of the issues might be Parallels. I have it installed, but it's not running. In the properties of Parallels I've set that all USB devices should be loaded in Mac.

My SD card slot on the latest MacBook (Mid 2012) won't mount my SD card. The SD card doesn't appear in Finder, Disk Utility, Image Capture or anywhere. I know it's not a software problem, because nothing changed before and after. How do I fix it?


I am trying to read a file that looks exactly like this  C   8230123345450 Simons      Jenny    R  0     12  C   3873472785863 Cartman     Eric     N  750   18  C   4834324308675 McCormick   Kenny    R  0     20   O   1384349045225 Broflovski  Kyle     -  6 //possible problem start  O   5627238253456 Marsh       Stan     T  3  To clarify: C = OnCampusStudents O = OnlineStudents  The code should determine whether the student is on campus or online then use the appropriate method and the read the code accordingly. It is crashing in my readOnlineStudent method on what i believe is the credits variable.   Throws an InputMismatchException.  I'm not sure what to try because everything looks right to me (obviously I'm missing something).  Here is the relative code:  private ArrayList<Student>readFile() throws FileNotFoundException {     ArrayList<Student> studentList;     studentList = new ArrayList<>();     Scanner in = new Scanner(new      File("C:\\Users\\KYLE\\Documents\\burger-cse205-      p02\\test\\input\\p02-students.txt"));      while(in.hasNext() == true){         String studentType = in.next();         if(studentType == "C"){             studentList.add(readOnCampusStudent(in));         }         else{             studentList.add(readOnlineStudent(in));         }     }     in.close();     return studentList; }  private OnCampusStudent readOnCampusStudent(Scanner pIn){     String id = pIn.next();     String lname = pIn.next();     String fname = pIn.next();     OnCampusStudent student = new OnCampusStudent(id, fname, lname);     String res = pIn.next();     double fee = pIn.nextDouble();     int credits = pIn.nextInt();     if(res.equals("R")){         student.setResidency(OnCampusStudent.RESIDENT);     }     else{         student.setResidency(OnCampusStudent.NON_RESIDENT);     }     student.setProgramFee(fee);     student.setCredits(credits);     return student; }  private OnlineStudent readOnlineStudent(Scanner pIn){     String id = pIn.next();     String lname = pIn.next();     String fname = pIn.next();     OnlineStudent student = new OnlineStudent(id, fname, lname);     String fee = pIn.next();     int credits = pIn.nextInt(); //this is the line that throws the error     if(fee.equals("T")){         student.setTechFee(true);     }     else{         student.setTechFee(false);     }     student.setCredits(credits);     return student; }   What can be done to fix this?  Thanks

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


I have a really long list in an itemize environment and I want to order it in alphabetical order. My code is the following:  \documentclass[letterpaper,openright,12pt]{article} %\usepackage[spanish]{babel} %Defino idioma como español \usepackage{graphicx} % Para Añadir imagenes \usepackage{subfigure} %Para las subfiguras \usepackage{caption} \usepackage{enumitem} \usepackage{multicol} \usepackage{float} \usepackage{caption} \usepackage{adjustbox} \usepackage{xcolor} \usepackage{setspace} \usepackage{rotating} \usepackage[spanish,onelanguage]{algorithm2e} \usepackage{algorithm2e} \usepackage{lscape}  \usepackage{tikz} \begin{document} \section*{Glosario} \begin{itemize}[leftmargin=*] \setlength\itemsep{0.00em} %\small \item \textbf{DD.HH:} Derechos Humanos \item \textbf{LH:} Logística Humanitaria \item \textbf{OMS:} Organización Mundial de la Salud \item \textbf{ONU:} Organización de las Naciones Unidas \item \textbf{WFP:} \textit{World Food Programme} \item \textbf{FIDA:} Fondo Internacional de Desarrollo Agrícola \item \textbf{ECHO:} \textit{European Civil Protection and Humanitarian Aid Operations} \item \textbf{CICR:} Comité Internacional de la Cruz Roja \item \textbf{ONEMI:} Oficina Nacional de Emergencias del Ministerio del Interior \item \textbf{IO:} Investigación de Operaciones \item \textbf{OFDA:} Oficina de Asistencia para Desastres del Gobierno de los Estados Unidos, América Latina y el Caribe. \item \textbf{CRED:} Centro de Investigación sobre la Epidemiología de los Desastres \item \textbf{NSGA:} \textit{Non-dominated Sorting Genetic Algorithm} \item \textbf{SPEA:} \textit{Strength Pareto Evolutionary Algorithm} \item \textbf{ONU:} Organización de las Naciones Unidas \item \textbf{ACNUR:} Alto Comisionado de las Naciones Unidas para los Refugiados \item \textbf{AG:} Algoritmos Genéticos \item \textbf{CONAF:} Corporación Nacional Forestal \item \textbf{CONASET:} Comisión Nacional de Seguridad de Tránsito \item \textbf{SNPC:} Servicio Nacional del Patrimonio Cultural \item \textbf{SIDCO:} Sistema de Información Digital para Control de Desastres \item \textbf{PIB:} Producto Interno Bruto \item \textbf{MINSAL:} Ministerio de Salud \item \textbf{SRT:} \textit{Standar Relief Time} \item \textbf{CAL:} Centro de Acopio Local \item \textbf{LS:}  Logística de Socorro \item \textbf{LD:}  Logística de Desarrollo \item \textbf{UNISDR:} \textit{United Nations Office for Disaster Risk Reduction} \item \textbf{ONG:} Organización no Gubernamental \item \textbf{VRP:} \textit{Vehicle routing problem} \item \textbf{PDSTSP:} \textit{Parallel Drone Scheduling Traveling Salesman Problem} \item \textbf{TSP:} \textit{Traveling Salesman Problem} \item \textbf{VIH:} Virus de Inmunodeficiencia Humana \item \textbf{SIDA:} Síndrome de Inmunodeficiencia Adquirida \item \textbf{ACO:} \textit{Ant Colony Optimization} \item \textbf{MPE:} Métodos de Programación Entera \item \textbf{VNS:} \textit{Variable Neighborhood Search} \item \textbf{MTZ-SEC's:} Miller-Tucker-Zemlin Subtour Elimination Constraints \item \textbf{CLT:} Costo Logístico Total \item \textbf{CTT:} Costo de Transporte Total \item \textbf{CIT:} Costo de Instalación Total \item \textbf{CAT:} Costo de Asignación Total \item \textbf{CDIT:} Costo por Demanda Insatisfecha Total \item \textbf{C:} Camiones \item \textbf{H:} Helicópteros \item \textbf{m-p:} Múltiples productos \item \textbf{m-v:} Múltiples vehículos \item \textbf{m-d:} Múltiples depósitos \item \textbf{s-d:} \textit{Split Delivery} \item \textbf{t-l:} Tiempo de circulación limitado \item \textbf{MO:} Múltiples Objetivos \item \textbf{TPDRO:} \textit{Transportation Problem in Disaster Response Operations}  \end{itemize} \thispagestyle{empty} \newpage  \end{document}    How can I do this? any ideas?. Thanks and advance and greetings.

I am wondering whether it is possible to display the items alphabetically regardless of the order we type on the backend? For example I am using itemize as follows:  \begin{itemize}     \item ISDYNSTP:  Is dynamic time step used?     \item ISCDCA:     \item MVAR     \item IS2TL_ \end{itemize}   But I want to display the items in the alphabetical order. I don't know whether it is possible or not. I have like hundreds of itemize items. Actually I am trying to create a glossary for the different parameters.


I had Windows 7 and Ubuntu on my hard drive working without any problems, but after installing a program called "Acronis True Image" and using its "try and decide" function, I lost GRUB.   How do I recover the Ubuntu installed on my hard drive? Do I use my USB device or CD?  Edit: Ok, thanks for your answers, but I think I was not very clear ... happens every time I run the application "Try and decide" from "Acronis True Image" I lose the GRUB, what I want is to boot the ubuntu operating system on my computer from my USB Device whenever I need it without having to restore the GRUB increasingly

I installed Windows 7, which ate Ubuntu's boot file. When starting up the computer, it now goes straight to Windows, without giving me the option of booting Ubuntu.   How can I get Ubuntu back?


I know that putting two resistors in parallel will double the wattage from the input to output, but only with half the resistance.  Example Parallel Circuit:         – Schematic created using   I know that putting two resistors in series will double the resistance, with the same wattage.            However: I need to double the wattage without the affecting resistance. Would this work?:

Is there anyway I can connect resistors to allow them to take more power such as using 4 1/4 watt resistors to get a 1 watt resistors. Or do i just have to use 1 1 Watt resistor.


How can I prove that nested sequence of non-empty bounded closed convex sets in Hilbert space have nonempty intersection?  I just don't know where to start.  Thanks

I read that in a complete Euclidean space - i.e. a normed real space with the norm induced by the scalar product - any sequence of nested bounded non-empty closed convex sets has a non-empty intersection, but I can't manage to prove it to myself. Has anybody any ideas or links to online proofs? Context The space is not assumed finite dimensional. At the point where I am in the text, Kolmogorov and Fomin's, they haven't defined a Hilbert space yet. I have not yet learned about the weak topology and reflexivity.


A $\pi^0$ consists of an up and anti-up quark. However, I also learned that when a particle and its anti-particle meet, energy is produced.  So, my question is that how can $\pi^0$ exist? Won't it turn to energy instantly if it is formed?

I have been taught that the $\pi^0$ particle contains either an up quark and an anti-up quark or a down and an anti-down. How can these exist without annihilating?  Also, it is its own antiparticle, but it doesn't make sense that the up version and down version would annihilate when they meet.  Or is what I've been taught a simplification - if so, in what state does this particle exist?


I came up with a question: What is the distribution of $(X−Y)^2+(Z−Y)^2$, where $X$,$Y$ and $Z$ are independent normal distributions with their own means and variance? The common part is $Y$ in both of the summands that introduces correlations, otherwise it is χ2. Thanks for the help!

I need to find the distribution of the random variable  $$Y=\sum_{i=1}^{n}(X_i)^2$$ where $X_i\sim{\cal{N}}(\mu_i,\sigma^2_i)$ and all $X_i$s are independent. I know that it is possible to first find the product of all moment generating functions for $X_i$s, and then transform back to obtain $Y$'s distribution. However, I wonder whether there is a general form for $Y$ like the Gaussian case: we know the sum of independent Gaussian is still a Gaussian, and thus we only need to know the summed mean and summed variance.   How about all $\sigma^2_i=\sigma^2$? Will this condition make a general solution?


I have tried print('\a') just to preduce a sound, but it didn't work. Why and How can I make it work? I'm on a linux system.

I'd like to have a python program alert me when it has completed its task by making a beep noise.  Currently,  I use import os and then use a command line speech program to say "Process complete".  I much rather it be a simple "bell." I know that there's a function that can be used in Cocoa apps, NSBeep, but I don't think that has much anything to do with this. I've also tried print(\a)  but that didn't work. I'm using a Mac, if you couldn't tell by my Cocoa comment, so that may help.


Although I have been visiting the Stack Overflow site for the past 20 days, until 18 day ago the Consecutive Days were shown properly but suddenly the next day it became 1 Day Consecutive.  Is there a bug with Consecutive Days counting? What can we do about it?

Yesterday I visited Stack Overflow and had 13 consecutive days visited.  Today, I visited and had 1.  Is this a bug?  Why did it reset?


As light is electromagnetic radiation. Then why I don't see any magnet bending light wave? Or why light doesn't diffract whenever it passes by a live wire?

Wikipedia article about Electromagnetic Radiation says "As an electromagnetic wave, it has both electric and magnetic field components". And  also confirms Light is EM wave.  Since we know that light travels through electromagnetic waves. Does that mean when we hold a Magnet close to the beam of a flashlight, it should interact with the waves and cause funny things to happen ?


Where can I find pre-built binaries for ? I do not want to have to build from source.  This is not a duplicate, because other answers don't give binaries, they just show how to compile from source.

Is there any way that still works to run OS X apps on Ubuntu 14.04? If Darling still works, please tell me how to install it.  Thanks. :)


Let's consider the function:   $$ f(x) = \frac {x^2 + x - 6}{x - 2} $$  At x = 2, the value fo the function is undefined, because $ x - 2 $ = 0. But if factor the expression on the numerator, we get $ \frac {(x + 3) (x-2)}{x-2} $, which on simplifying yields $ x + 3 $. At $ x = 2 $, the function gives 5, which is not what we get before simplifying.   If all we do too the initial function is simple algebraic manipulation, shouldn't both functions yield the same value?

$$\lim _{x\rightarrow 5}\frac{x^2-25}{x-5}  = \lim_{x\rightarrow 5} (x+5)$$  I understand that to evaluate a limit that has a zero ("hole") in the denominator we have to factor and cancel terms, and that the original limit is equal to the new and simplified limit. I understand how to do this procedurally, but I'd like to know why this works. I've only been told the methodology of expanding the $x^2-25$ into $(x-5)(x+5)$, but I don't just want to understand the methodology which my teacher tells me to "just memorize", I really want to know what's going on. I've read about factoring in abstract algebra, and about irreducible polynomials (just an example...), and I'd like to get a bigger picture of the abstract algebra in order to see why we factor the limit and why the simplified is equal to the original if it's missing the $(x-5)$, which has been cancelled. I don't want to just memorize things, I would really like to understand, but I've been told that this is "just how we do it" and that I should "practice to just memorize the procedure." I really want to understand this in abstract algebra terms, please elaborate. Thank you very much.


The "polarization identity" constructs an inner product from a norm provided the parallelogram law is met by the norm. How does the term originate, i.e. what has this to do with "polarization" ?    (For reference:   Polarization identity (real space): $\langle v, w \rangle = ¼(||v + w||^2 - ||v - w||^2 )$ Polarization identity (complex space): $\langle v, w \rangle = ¼(||v + w||^2 - ||v - w||^2 + i||v + iw||^2 - i||v - iw||^2)$ Parallelogram law: $2||v||^2 + 2||w||^2 = ||v + w||^2 + ||v - w||^2$

The polarization identity expresses a symmetric bilinear form on a vector space in terms of its associated quadratic form:  $$ \langle v,w\rangle = \frac{1}{2}(Q(v+w) - Q(v) - Q(w)),  $$ where $Q(v) = \langle v,v\rangle$. More generally (over fields of characteristic $0$), for any homogeneous polynomial  $h(x_1,\dots,x_n)$ of degree $d$ in $n$ variables, there is a unique symmetric $d$-multilinear polynomial $F({\mathbf x}_1,\dots,{\mathbf x}_d)$, where each ${\mathbf x}_i$ consists of $n$ indeterminates, such that $h(x_1,\dots,x_n) = F({\mathbf x},\dots,{\mathbf x})$, where ${\mathbf x} = (x_1,\dots,x_n)$. There is a formula which expresses $F({\mathbf x}_1,\dots,{\mathbf x}_d)$ in terms of $h$, generalizing the above formula for a bilinear form in terms of a quadratic form, and it is also called a polarization identity.  Where did the meaning of "polarization", in this context, come from? Weyl uses it in his book The classical groups (see pp. 5 and 6 on Google books) but I don't know if this is the first place it appeared. Jeff Miller's extensive math etymology website doesn't include this term. See .


I created an image for a desktop wallpaper and set the image directly in Windows (not from a browser). However, the image file I made is no longer on my computer, but the wallpaper is still there. How can I retrieve this wallpaper? It has to load from somewhere.

I run Windows XP and the wallpaper I used to have got lost. I have backups of the system itself, so if I knew where to look, I could find a copy of the old wallpaper.  I have some idea of the original filename (searching now), and I recall it saves it as a bitmap, but an exact location would be helpful.  It was a photo/JPEG that used to be on the filesystem, and I don't have backups, so the Firefox, and Internet Explorer wallpaper locations are unlikely. I checked %SYSTEMROOT%\system32 as well - so I'm assuming it's somewhere else.


I'm trying to create a class (Team) but I'm getting a nullpointer error This is where it's called  Team[] Teams = new Team[6];    private void AddTeamButtonMouseClicked(java.awt.event.MouseEvent evt) {                                                    String InputTeamName = TeamNameInput.getText();          switch(TeamCounter)         {             case 0:                 Teams[TeamCounter].Name = InputTeamName;                 Team_1.setText(Teams[TeamCounter].Name);                 TeamCounter++;                 break; }   Team Class  public class Team  {     String Name;     Player[] Players = new Player[5]; }

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


Is a monk's Slow Fall ability considered magical? That is if a monk were to enter an antimagic field whilst falling, would their slow fall ability be negated by the antimagic field, the same way some Ki abilities would be?

Often confusion arises when the  spell is used, an  is worn, or the 's anti-magic ray is employed, whether a given character's ability will still function.   The spell does give you some guidelines on how to adjudicate the effects of the loss of magic but says very little about how to determine what is affected.  In short, how do I tell if an ability is magical?


I had a train ticket from Antwerp Central to Schipol Airport on Thalys in the evening, connecting to a KLM flight from Amsterdam to Mumbai, operated by Jet Airways the next day.  I collected the ticket in the morning but have missed the Thalys. As my flight is the next day I'm thinking of catching a train tomorrow and going to Schipol.  Will they let me check in?

I have a flight booked form Cairo to Amsterdam Schiphol via KLM and then a Thalys train from Amsterdam Schiphol to Brussels. As Brussels is not my final destination anyway I want to intentionally skip the train from Amsterdam airport to Brussels Midi. I have read many reviews about skipping a flight leg can lead to cancelling your entire flight but does the train booked with the flight included in this rule? What are the risks?