I have the Steam Launcher installed (installed via Software Center), when double-clicking the launcher the following is executed in the command window:  Steam needs to install these additional packages:  libgl1-mesa-dri:i386, libgl1-mesa-glx:i386  Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  libgl1-mesa-glx:i386 : Depends: libglapi-mesa:i386 (= 10.1.3-0ubuntu0.4)  unity-control-center : Depends: libcheese-gtk23 (>= 3.4.0) but it is not going to be installed                         Depends: libcheese7 (>= 3.0.1) but it is not going to be installed E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.  Press return to continue:    Upon pressing Enter, the following dialogue box pops up:  You are missing the following 32-bit libraries, and Steam may not run: libGL.so.1    What to do?

I am not sure what caused this error, but here is what the whole error says, and also this is sitting as a notification, and preventing me from updating any software using Update Manager - Please provide some assistance or tell me how to figure out what to do to fix it.  Could not calculate the upgrade  An unresolvable problem occurred while calculating the upgrade.  Please report this bug against the 'update-manager' package and include the following error message: 'E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.'


I am looking for a material that is total dark, something that even when you illuminate it with flash light you will not get any light back. it exists? or is it possible to make one such material?

Black is the absence of light because it absorbs light, but when we create black paint or black objects, light is always reflected, either in all directions in matte or smoothly in shiny black objects, making it never a true black. Would it be possible to use polarization to create an object that does not reflect any light, creating a truly black substance, without any shadows or reflection of light?


I have enough experience with electronics to design and solder working circuits. I never quite understood though why circuits must be closed for current to flow.  I alway understood electrical current as the movement of charged particles (free electrons usually in circuits), from a ‘high pressure’ region to a ‘lower pressure’ region.  But by that analogy I never could comprehend why no current flows when the - pole of one battery is connected to the + pole of another battery?  Please don’t say “because the circuit isn’t closed”. It’s exactly what I’d like to understand - on a physical level - why the circuit must be closed (especially when understanding electrical current as the flow of charged particles from high-density to low density)

In other words, why do we need to connect the battery positive to the negative to get electron flow? As far as I know, voltage difference is what drives current flow.  From what I understand, there's a surplus of negative charge (electrons) in the positive end of a battery (weird I know, but I guess they do it for mathematical reasons). Between the positive and negative ends of the battery is some kind of wall that prevents the electrons from diffusing, so they have to go the long way (through a wire to the other end of the battery) to diffuse and reach the receiver atoms/molecules.  So why not just have the surplus of electrons on one end go to ground to equalize (e.g. 5 volts to 0 volts should produce current)? Why does it have to be the other end of the battery? I'm sure there's atoms/molecules in the ground that could accept the extra electrons (receivers atoms/molecules for the donors in the battery).


TLDR; I already know how to use design software but I don't know how to design. Bottom Line: Is there a specific sequence to follow for a proper education in the soft skills of design (theory, concepts, process, etc.)? Background I'll start with a little background about me to show the motivation about the question, isn't really necessary to answer the question. I'm 23 years old and finishing my degree on engineering informatics. When I was 14 years old, I learn HTML/CSS. I can use a lot of Adobe Suite software to make a lot of things (PS, AI, Pr, etc..). Then, as time passed by, I started learning some computer science oriented things. I can make a website really fast, etc.. But, my problem is, I'm not in some kind of "design thinking". I like design (if I weren't getting an engineering degree I probably would have gotten a design degree). I like design a lot, and I would love to learn more of design. I would love to make "pretty things" by my own, as a designer does. But I can't study to get a design degree due to my priority list (I want to achieve other goals more in this moment of my life), but what I really want is to learn some design on my own. Long form question Is there some way to emulate a design degree/program with books and others static resources? In my 6 years of study I have taken everything from books. My teachers made everything faster, but I don't think that passing through a computer science degree was really necessary: books + internet + practice told me almost 95% of what I learned there. But there is a problem, as you can see in this question: . There are good books and bad books. And frankly, a lot of bad books. I didn't find a reliable list of design books. There are a lot of blogs with "list of books to learn things", but most of them are really just a list taken from somewhere else... For example, I could read this list , but I need to go in order, starting from the basics. So for that I could take graphic design courses, like this:  (or any other program, it's just an example) and try to learn from the topics that the program shows, but it is still unclear about what I should learn because there isn't, for example, a course in "color theory". They are more like "design I", "design II", "design III". I think I'm gonna need to search for the syllabus for a particular course. I really want to improve my design skills, but I don't want to get a degree in it.  I've been an autodidact all my life (see background) and at this point, I ask: My research I have searched a bit about this, and here on StackExchange there are a lot of question that are close, but not getting to the heart of the issue. : The answer is just a "look at those website's" (And okay, this could help a bit, but I don't think one will get to a degree level just looking on some websites, or it is?). : 2 or 3 books to learn design, the same as above. This could help a bit, but won't get me to a degree-equivalent level (I'm looking for something more like computer science's courses which have their own book for the topic. Does something like this exist in graphic design?). : This could be the same question that I have, but the answer didn't satisfies me, I need a lot more detail (for example, more books or guides to follow). DISCLAIMER  does not answer this question. It's the first question to answer before getting to this one.

Is it required for people to go to design schools to become a Graphic Designer? I've heard many cases where they have started from scratch without previous education in design and are doing fine as freelancers/working in studios.  Would it be better to go to a design school to become a Graphic Designer? How much leverage would it give you if you went to one?


Hello i recently tried to install steam on ubuntu on 64-bit desktop version didn't work ,so i tried server version 64-bit still didn't work. I saw somebody say that steam is only 32-bit so i tried 32-bit server version but still got same result. I use  Raspberry Pi 4 Model B; 4 GB, ARM-Cortex-A72 4 x, 1.50 GHz, 4 GB RAM.    ubuntu@ubuntu:~$ sudo apt install steam Reading package lists... Done Building dependency tree        Reading state information... Done Package steam is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source However the following packages replace it:   steam-devices  E: Package 'steam' has no installation candidate  so i tried this solution:  didn't work ubuntu@ubuntu:~$ sudo dpkg --add-architecture i386 ubuntu@ubuntu:~$    i am stuck here a don't know what to do.

I am having trouble opening the  client after I have already installed it. I am using . I have installed Steam directly from their website. When I try to open steam, it says: Steam needs to install these additional packages: libgl1-mesa-dri:i386, libgl1:i386, libc6:i386  and asks for my password. I put it in, but now it says: .......... Reading package lists... Done Building dependency tree Reading state information... Done E: Unable to locate package libgl1-mesa-dri:i386 E: Unable to locate package libgl1:i386 E: Unable to locate package libc6:i386 Press return to continue:  I press the return key, it starts running, but then it stops loading and a window pops up that says:  You are missing the following 32-bit libraries, and Steam may not run: libc.so.6  What should I do? I just started using Ubuntu this past week.


I have a SharePOint library for which there are about 5 content types added. Some users do drag and drop files in the library and because of that the Content type value for these files is set to the default one.  When I go into Quick edit (added content type in the view), I am unable to change the set content type but when I do files>Edit properties, it does allow me to change the content type.  Is this the default behavior or is there something we can do allow users to change content type in the quick edit view.  Thanks in advance.

When you drag and drop single / multiple files into a document set / library, SharePoint just add values to the required fields and a check the file out.   I've tried to use quick edit but it does not work to change content type. The only way is to edit properties and then check it in.  Is there a quicker way to change content type on a single file?


Does anyone have examples in mind that following statements are true for vector spaces over a division ring, but need not be true for modules over an arbitrary ring?  Every maximal linear independent set in a free module is a basis. Every minimal spanning set in a free module is a basis. Every quotient of a free module is free.

Linear algebra is a very well-behaved part of mathematics. Soon after you have mastered the basics you got a good feeling for what kind of statements should be true -- even if you are not familiar with all major results and counterexamples.  If one replaces the underlying field by a ring, and therefore looks at modules, things become more tricky. Many pathologies occur that one maybe would not expect coming from linear algebra.  I am looking for a list of such pathologies where modules behave differently than vector spaces. This list should not only be a list of statements but all phenomena should be illustrated by an example.  To start the list I will post an answer below with all pathologies that I know from the top of my head. This should also explain better what kind of list I have in mind.


Trying to remember the title of a short story about an AI robot computer who kills all humans out of resentment, but keeps a small group to torture. The group consists of one loner, who eventually saves the rest of the group by murdering them with an icicle, i think. The AI is very angry the others were saved, and eternally tortures the lone survivor, turning him into this jelly glob thing.

I can't remember the title of a story that I wanted to read lately. I know the plot was as follows: An AI controls the last few remaining humans and later they are forced to live in a cave. One of them tries to escape and he is turned into some kind of goo by the AI.   Do any of you recognize it?


How to prove that  is not a topological manifold.I think I have to do something with the meeting point of the two cones.

My question is that   A double cone ( also named as "circular cone") is not a surface.   I know its reason. But I cannot show this mathematically.     Suppose $\sigma : U \to S\cap W$ Is a surface patch.   Because the vertex $(0,0,0,)$ is a problem,  S is not a surface.   I can see it. But I cannot express it in the mathematical way.   When I remove the vertex point $(0,0,0)$, the double cone is a surface.   Please can someone show/write these mathematically?


What is endurance used for in Fallout Shelter? The storage room says it uses Endurance, but what does that mean? It doesn't produce anything so what is the advantage or putting a dweller in there?

Besides its workplace uses, like Charisma in Living Quarters, Strength in Power Generators, Agility in Diners.   Do we know if Endurance increases HP in the Dwellers, or that strength helps in melee damage / survivability in the wastelands? And Perception?


How do you prove from Maxwell's equations that the speed of light is independent of the motions of the sources that produce the wave?

I've been told that, from Maxwell's equations, one can find that the propagation of change in the Electromagnetic Field travels at a speed $\frac{1}{\sqrt{\mu_0 \epsilon_0}}$ (the values of which can be empirically found, and, when plugged into the expression, yield the empirically found speed of light)  I'm really not sure how I would go about finding $v = \frac{1}{\sqrt{\mu_0 \epsilon_0}}$ simply from Maxwell's equations in the following form, in SI units --  $$\nabla \cdot \mathbf{E} = \frac {\rho} {\epsilon_0}$$  $$\nabla \cdot \mathbf{B} = 0$$  $$\nabla \times \mathbf{E} = -\frac{\partial \mathbf{B}} {\partial t}$$  $$\nabla \times \mathbf{B} = \mu_0 \left( \mathbf{J} + \epsilon_0 \frac{\partial \mathbf{E}} {\partial t} \right)$$  Is what I believe true? (that the speed of propagation is derivable from Maxwell's Equations)  If not, what else is needed?  If so, can you provide a clear and cogent derivation?


I hear in many articles the word parameters and hyperparameters but I don't know what they mean by that. Are they variable or the weights of the nodes?  explain me in an intuitive way as an analogy please

Can anyone give me full details about what we mean by hyperparameters, and what in the Dirichlet distribution are called hyperparameters? A practice example for the estimation of those parameters would also be useful.


public Node searchData(String fullName) {     Node current = root;     while(current.fullName != fullName)     {         if(fullName.compareTo(current.fullName) < current.fullName.compareTo(fullName))         {             current = current.leftChild;         }         else if(fullName.compareTo(current.fullName) > current.fullName.compareTo(fullName))         {             current = current.rightChild;         }         else             current = null;     }      return current; }   Whenever I enter a name into the program I receive a null pointer exception error. The program itself initializes a binary tree with a text-file and that already works but i'm not sure why it keeps crashing when I try to search for the node itself. I know the nodes already exist but can't figure out why it says that its null.

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?


Suppose I fly to France and stay for 90 days. Then I cross into Spain by land, then fly to the Netherlands, then go to Norway. So the total trip length is much longer than 90 days. As long as I stay less than 90 days in each country individually, can I just take my American passport and not worry about anything? Or do I have to do some paperwork?

I have searched the web a lot and could not find an answer that fits my situation. Here are two links that are quite contradictory:       My situation:  I've visited Portugal in December 2012 for 29 days on a Schengen visa valid from December 1st, 2012 to February 1st, 2013 for research purposes (I am a Ph.D. student). I want to visit Sweden from February 10th, 2013 to May 10th, 2013 (89 days). I have applied for a Schengen visa again (for research). How will the 90/180 rule work in my situation?


I want to install AOKP on my Vodaphone Samsung Galaxy S5 mini SM-G800F, however, the kminilte ROM is not yet developed.   klte seems the closest to kminilte, so will installing it brick my phone, or will it be successful? What features of my hardware will be voided by installing the wrong version if it successes?    Edit as I cannot add an answer as this question is a duplicate.  I actually started dabbling in things regarding porting (slightly modifying ROMs for different devices). And the differences are huge. In the script that initializes the rest of the system, it tests for different models of klte, thus not finding a result and not booting.  Regardless of that, the CPU, screen size, pixel density etc. is different.  If someone has an unsupported device, they can try to find the most similar supported devices to keep change to minimum. You can also look on the CM wiki for unofficial ports.   When comparing devices, I recommend the webpage  as it gives very detailed info about android phones.

I own a MicroMax A100. I want to install the latest version of a different ROM (Samsung or Nexus).  Is it possible? If so, can you tell me how?  If not, can I install a ROM made for a different device, but from the same manufacturer? For example, could I install a ROM for the MicroMax A110, which is the successor of A100?


Let $G$ be a finite abelian group with exactly one element of order $2$ denoted by $\alpha$. Prove that $\prod_{g \in G} g = \alpha$  Okay so I was given two hints for this problem  Hint 1 : If $g \in G$ doesn't have order $2$, then $g \neq g^{-1}$ Hint 2: If you write out $0+1+2+3+4+50+1+2+3+4+5 \mod 6$, why does it come out $3$, other than computing brute force?  I'm not sure at all how to use hint 1. The answer for Hint 2 is that you can pair up $5+1=6$ and $4+2 = 6$ and be left with $3$. In that hint we are looking at the additive group $\mathbb{Z}/6\mathbb{Z}$, and we have $|5| = |1| = 6$ and $|4| = |2| = 3$, so this hint would suggest looking at group operating each two elements of $G$ which have the same order with each other. But the problem is, is that even though $G$ may be a finite group, some $g \in G$ may have $|g| = \infty$, and furthermore every $g \in G$ may have a unique order, (please correct me if I'm wrong). So I'm not sure how I could use it to prove $\prod_{g \in G} g = \alpha$ At this point all I can say about $G$, is that by Lagrange's Theorem, $|G| = 2k$ for some $k \in \mathbb{Z}^+$, and that (trivially) letting $\alpha \in G$ be the element of order $2$, we have $\alpha = \alpha^{-1}$. I'm assuming there's some algebraic trick that I'm missing here, because I'm sure all I'd have to do is just write out $$\prod_{g \in G} g = g_1 \cdot g_2 \cdot \ ... \ \cdot g_{2k}$$ and find some way to simplify this expression. EDIT: Thanks to the comments and answers below I realized that since $G$ is abelian, and for any $g \in G$, we have $g^{-1} \in G$, so $\prod_{g \in G} g = g_1 \cdot (g_1^{-1}) \cdot ... \cdot g_i \cdot(g_i^{-1}) \cdot ... \cdot (g_k) \cdot (g_k^{-1})$ where for some $i \in \{1, ..., k\}$ we have $g_i = \alpha$, but now I don't see why $\prod_{g \in G} g \neq e$ where $e$ is the identity of $G$?

Let $G$ be an finite abelian group, define $s= \Pi_{g\in G} g$, show that $s = e$ unless $G$ has exactly one involution $u$, in this case $s=u$.   I have the start of a proof, but I get stuck at a point.   Proof  Write $G$ as $G = \{e\} \cup I \cup \{g_1, g_1^{-1}, \ldots, g_n, g_n^{-1}\}$ where $I$ is a set of the all the groups involutions.  Since $G$ is abelian $\Pi_{g\in \{g_1, g_1^{-1}, \ldots\}} g = e$ we just need to examine $\Pi_{u\in I} u$  Now:   If $|I|=0$ then the theorem holds, If $|I| = 1$ then $I=\{u\}$ and $s= u$, the theorem holds If $|I| = 2$, requires closer examination:  Let $I = \{u_1,u_2\}$ be the set of all involutions (not equal to $e$), then $u_1u_2$ is also an involution (since $G$ is abelian).   If $u_1u_2 =e$ then $u_1=u_2$, contradiction, if $u_1u_2 = u_1$ then $u_2=e$, contradiction. $u_1 u_2=u_2$ results in the same contradiction. This means that the case $|I|=2$ is not possible. the case $|I|=3$ is possible, let $I = \{u_1,u_2,u_3\}$ then it's easy to prove $u_3 = u_1u_2$. The theorem holds.   How should I continue? I've tried splitting $I$ as   $$I=\{u_i: u_i \not = u_ju_k (\text{for a certain }j\not = k)\} \cup \{u_i = u_ju_k (\text{for a certain} j \not = k)\}$$ but I still get stuck.  Also the case $|I|= 4$ seems contradictory once again..


I'm a little concerned about using the WHERE query within my PHP code, I've created the query and everything works perfectly - however i'm not the best with security issues, particularly the possibility of injections and cross-site scripting.  This is the code i'm currently using on my test site:  $sql = "SELECT address FROM shops WHERE shopname='name'";  if($res = mysqli_query($link, $sql)){  if(mysqli_num_rows($res) > 0){ ; while($row = mysqli_fetch_array($res)){  echo ".....   There's no user inputs on any part of the website, if anyone can see an obvious error in my coding and has any recommendations that would be great!  Thanks in advance!

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


I have a batch file that runs at startup with admin privileges (using Task Scheduler) and does some maintenance tasks. However, there is a problem. I have a certain maintenance task I need to do which must run as non-admin. If it runs as admin, it doesn't work. (It doesn't matter for our purposes what the task is or why it doesn't work as admin. I'd like to keep the question general so it can be useful for other people with a similar problem, regardless of the specific task.) Now, of course, I could just set up a separate task in the Task Scheduler that runs without admin privileges, which will do only that specific task. But I want to do several tasks in a specific order, some of them require admin privileges and some don't. So to summarize, the question is: can I execute a command without admin privileges from within a batch file that is already running with admin privileges?

Is it possible to run a command without elevated privileges from batch file that was run with elevated privileges?


I'm currently running Ubuntu 16.10 from an external drive which I'm using as my main drive. I need to format the drive to install Windows 7, but this laptop doesn't have a cd drive.  I made a bootable usb with windows 7 and wasn't able to install because this version doesn't have the disc repair options and the installation menu won't let me format the drive.

I'm trying to install Windows 7 with a 4GB flash drive, but my error that comes up is that my hard drive I'm trying to install on is in ext4. I need to format it to read NTFS. I can't seem to find any topics on how to format an active hard drive. I found a topic that explains how to move Ubuntu to a new drive, but it's a bit confusing to me.


What is the meaning of the notation $\mathbb{C}^\times$ where  $\mathbb{C}$ is the usual set of complex numbers? The context is that of continuous functions of the torus $\mathbb{T}=\mathbb{R}/\mathbb{Z}$ that are  $\mathbb{C}^\times$-valued.

I'm doing some sheets for my Abstract Algebra class and I can't seem to remember the group defined as $\mathbb{R}^{\times}$. It's obviously some variation of $\mathbb{R}$ but I'm away from college on reading week so can't ask my tutor. If someone could clear up the confusion I'd be grateful.


I need to concatenate two variables to create a filename that has an underscore. Lets call my variables $FILENAME and $EXTENSION where filename is read from a file.  FILENAME=Hello EXTENSION=WORLD.txt   Now...  I have tried the following without success:  NAME=${FILENAME}_$EXTENSION NAME=${FILENAME}'_'$EXTENSION NAME=$FILENAME\\_$EXTENSION   I always get some kind of weird output. Usually the underscore first.  I need it to be  echo $NAME Hello_WORLD.txt

I need to concatenate two strings in bash, so that:  string1=hello string2=world  mystring=string1+string2   echo mystring should produce     helloworld


I recently bought shares on a market where I normally buy and we're confirmed at asked price sorry not bid please see attached pictures and number of shares were confirmed and a congratulations note sent as normal but at open time price was changed but I screenshot my buying price each time. Can they do that Ask one price and confirm number of shares when you buy but later changed it? What is want to know is that legal?


claims that adding baking soda is crucial when soaking chickpeas. Is this true, and if so, what is the reason that this works?

My recipe for hummus says to cook the garbanzo beans with a little baking soda to soften them. Does this work with other legumes?   I've often seen the advice against salting the cooking water for beans, as it supposedly toughens them. Will a different sodium compound, bicarbonate, have the opposite effect?   Would love to know the science of this issue.


I'm learning to integrate and was asked to integrate $\int\frac{1}{1+\sin x}dx$ I get the answer $-\frac{2}{\tan\frac{x}2+1}+c$ which Symbolab confirms is correct, but the textbook says the answer is $\tan x-\sec x+c$. I can't seem to transform my answer to that one using trig identities. Any idea how/if one can get that result? Many thanks, Andrew

For $\int \frac {1}{1+\sin x} \mathrm{d}x$, my calculus textbook told me to multiply the integrand by $\frac {1- \sin x}{1- \sin x}$ to obtain: $$ \int \frac{1-\sin x}{1-\sin^2 x} \mathrm{d}x= \int \frac{1-\sin x}{\cos^2 x} \mathrm{d}x$$  From here, it is a matter of breaking up the integral to two very trivial integrals, $\int \sec^2x \mathrm{d}x$ and $\int \sec x \tan x \mathrm{d}x$, which are easily found via commonly known rules.  My question is whether there exists a way of finding $\int \frac {1}{1+\sin x} \mathrm{d}x$ without having to perform the multiplication by $1- \sin x$ in the numerator and denominator.


Let $r>4$ be a positive integer. I want to solve this difference equation:   $$u_{n+1}-r²(1+r²ⁿ⁺¹)u_{n}+r²r²ⁿ⁺¹u_{n-1}-2r²r²ⁿ⁺¹=0$$ but I have no a good idea to start.

Let $r>4$ be a positive integer. Let us consider this difference equation: $$u_{q+1}=(r^{2q+1}+(c/a))u_{q}-(c/a)r^{2q-1}u_{q-1} +2c+d-(bc/a)$$  where $a,b,c,d$ are integers.  I want to find a closed form, but I am not able to find the good idea. Or at least how we can prove that a solution exists.


I have a file containing population information for a bunch of towns. I have another file that is a list of the names of a subset of those towns. I want to select the population information from the first file using the second file. How would I do this?  Examples:  File 1: ma-towns.txt  Acton   Town    Middlesex   Open town meeting   21,924  1735   Acushnet    Town    Bristol Open town meeting   10,303  1860   Adams   Town    Berkshire   Representative town meeting 8,485   1778   Agawam  City[4] Hampden Mayor-council   28,438  1855   Alford  Town    Berkshire   Open town meeting   494 1773   Amesbury    City    Essex   Mayor-council   16,283  1668   Amherst Town    Hampshire   Representative town meeting 37,819  1775     File 2: town-list.txt  Acton   Adams   Agawam    Desired output would be  Acton   Town    Middlesex   Open town meeting   21,924  1735   Adams   Town    Berkshire   Representative town meeting 8,485   1778   Agawam  City[4] Hampden Mayor-council   28,438  1855      Basically, as said generally, extract the line if it contains the string in one of the lines of file 2.

I have two files in  file A, there are sequence_numbers in the other file B, there are many columns, and the first column is sequnce numbers, I want to get a files with all the lines in the B with the sequence numbers which are in the A how can I achieve this? thanks  like file A  1 3 8 9 20   file B  1 kfjk 3243424 2 fkdkf 23543592 3 iefjk 21493402 7 dlafdl 23435231 8 kfkdlkf 309834


I try Ubuntu 14.04 by using live CD and I logout that and now I can't login again because it asks me input username and password. I don't know what I should enter the usename and password.

When I boot Ubuntu 10.04.3 from a live CD, it asks me to enter a username and password. I have not booted before, and I haven't created an account.


Let X be a topological space. Prove that X is a T2-space if and only if $A = \{ (x,x) : x \in X \}$ is closed in $X \times X$.  I've been able to prove first part of the result but not the converse.  For the first part,  We have X is T2. hence X x X is also T2. Hence X x X is T1.  Then for any z belonging to A and y not belonging A, there exist an open set U in X x X such that y belongs to U but z doesn't belong to U.  Hence for every z belonging to A and for a fixed y not belonging to A , there exists an open set V(y) in X x X such that "V(y) intersection A" is empty.  hence (X x X) - A = Union of all V(y)'s such that y doesn't belong to A.  since arbitrary union of open sets is open, hence (X x X) - A is also open in X x X , Implying that A is closed in X x X. ( Is this proof valid ? )  Now how to prove the converse part ?

Let $X$ be a topological space. The diagonal of $X \times X$ is the subset $$D = \{(x,x)\in X\times X\mid x \in X\}.$$   Show that $X$ is Hausdorff if and only if $D$ is closed in $X \times X$.   First, I tried to show that $X \times X \setminus D$ is open using the fact that $X \times X$ is Hausdorff (because $X$ is Hausdorff), but I couldn't find an open set that contains a point outside $D$ and is disjoint to it...


The anime has ended at episode 24, "Akame ga Kill!".  Does the manga continue the story beyond the anime's conclusion?

I saw there are various manga with Akame ga KILL! in their names.  The ones I have found are:       Which one should I read if I want to continue the storyline of the anime?


How can i resolve this problem? I can not enter in linux partition without loosing any data..

I upgraded my kernel today with ukuu, and since then I cant boot because i'm getting this errors:   error: /boot/vmlinuz-4.18.12-041812-generic has invalid signature error: you need to load the kernel first   I have dual boot with windows 10 and ubuntu 18.10 (Upgraded today)  Update: I managed to boot to older kernel that i chose from "Advanced  options for Ubuntu" in grub  But I need to upgrade my kernel and if I do that I still get the same problem...


I read content of the file into variable like this  var=$(<somefile)   But if the file doesn't exist I get accordingly an error message  bash: somefile: No such file or directory   Is it possible to redirect stderr to >/dev/null without using cat command?

I want to replace cat:  var=$(cat "filename" 2>/dev/null)   by bashism syntax:  var=$(<"filename")   The problem is that I don't know how to make the bashism silent to avoid such warnings:  bash: filename: No such file or directory   I've tried this:  var=$(2>/dev/null <"filename")   but it does not read existing files into var anymore.


I need some help with starting this problem. I am given that $$C=\left\{\left( \begin{array}{cc} a & b \\ -b & a \\ \end{array} \right): a,b\in\mathbb{R}\right\}$$ is a subring of the ring of all $2\times2$ matrices with real number entries, with respect to usual addition and multiplation of matrices. My task is to show that $C$ is isomorphic to the field $\mathbb{C}$ of complex numbers.

Below is an example from I.N. Herstein:       Let  $R=\Bigg\{\left( \begin{array}{ccc} a & b \\ -b & a \end{array} \right)\Bigg|a,b\in \mathbb R\Bigg\}$ and let $\mathbb C$ be the field of complex numbers. Define $\psi :R\to \mathbb C$ by $\psi\left( \begin{array}{ccc} a & b \\ -b & a \end{array} \right)=a+bi.$       It is asked to prove that $\psi$ is a ring isomorphism of $R$ onto $\mathbb C$ .    can anyone help me with some hint how to prove the ring isomorphism.


The $U_e$ and $U_o$ denote the set of all real-valued even/odd function on $\mathbb R$ respectively.

A function $f : \mathbb{R} \rightarrow \mathbb{R}$ is called even if $f(-x) = f(x)$ $ \forall x \in \mathbb{R}  $   A function $f : \mathbb{R} \rightarrow \mathbb{R}$ is called odd if $f(-x) = -f(x)$ $ \forall x \in \mathbb{R}  $   Let $U_{e}$ denote the set of real-valued even functions on $\mathbb{R}$ and let $U_{o}$ denote the set of real valued odd functions on $\mathbb{R}$.   Show that $\mathbb{R}^{\mathbb{R}} = U_{e} \oplus U_{o}$   This question from Q24 of "Linear Algebra Done Right" 3rd Edition - Chp 1.4 (Subspaces). The author of the book does minimal work with functions during the chapter. I have no idea how to approach the question.


I have already seen , but this is slightly different.   I have a rather complex Tikz image, which I'd like to eventually include in a Latex document; as such, I'd like this .tikz file to be as self contained as possible. There are a bunch of commands in there relevant to building the plot; unfortunately if I leave them as-is, I get  (even in a standalone .tex file). Specifically, if the commands execute between {document} and {tikzpicture}, then the extraneous space is generated; I could have the commands in preamble, but then the .tikz file will not be self-contained.  So, I thought I'd collect these commands in a \def subroutine, and have them run inside the {tikzpicture}. Unfortunately, one of those commands is \widthof, which I intended for measuring the width of the text "256" in the tiny font, and wanted to use that to set the x scale of the pgfplot. So I came to this MWE:  % \documentclass{article} \documentclass{standalone}  \usepackage{calc} %\widthof \usepackage{pgfplots} \pgfplotsset{compat=1.5.1} \usetikzlibrary{pgfplots.groupplots} \usepackage{pgfplotstable}  \pagecolor{yellow!15}  % \newcommand\prepCmds{ \def\prepCmds{   \newlength{\smlblwtmp}   \setlength{\smlblwtmp}{\widthof{\tiny 256}}   \global\let\smlblwid\smlblwtmp   \typeout{smlblwid FIRST: \the\smlblwid} }  % \prepCmds{} % smlblwid FIRST: 10.2085pt  \begin{document}  % \prepCmds{} % smlblwid FIRST: 10.2085pt  \begin{tikzpicture}    \prepCmds{} % smlblwid FIRST: 0.0pt    \begin{axis}[     x=2*\smlblwid,   ]     \addplot {x*0.5};   \end{axis}  \end{tikzpicture}  \end{document}   As it can be seen, only when I call the \prepCmds inside {tikzpicture}, the \widtgof fails and returns 0 (everywhere else, it returns a correct number); when that happens, pdflatex shows this:   PGFPlots warning: The ticklabel anchor cannot be determined, the normal vector  -(0.0pt,-1.0pt) and the unit y vector (0.0pt,1.00005pt) are almost parallel (ab s(cos(angle)) = 1.00005pt)! pgfplots@borderanchor@for@axis 1,2,3: y, 1v0, rectangle   One would say, as expected for x unit of 0 - but it took me hours to debug this so far: among other things, I inserted a \message in the pgfplots source so the arguments of \pgfplots@borderanchor@for@axis are plotted  (when the width is not zero, with \prepCmds running elsewhere, the arguments are x, v00, rectangle).   Obviously, all this boils down to \widthof returning 0 inside a {tikzpicture}; now that I know this, I guess I could move just the \widthof calculation out of the subroutine. However, I'd still prefer for the \widthof calculation to be inside the subroutine, for self-containment reasons, so I would like to ask: why is \widthof inside a {tikzpicture} zero; and is there some sort of a trick (maybe "globalize" some tikz intern variables?) that would make \widthof work inside a {tikzpicture} properly?

I'm trying to use an \hbox to measure the dimensions of a certain text. This is working in normal text as in the following example: \setbox37=\hbox{this is a text that I want to measure} text width is \the\wd37, text heigh is \the\ht37\\ text contents: \box37  The output is correct as I expected: text width is 159.63913pt, text heigh is 6.94444pt text contents: this is a text that I want to measure However, when trying to do the same inside a TikZ environmnet, the box I'm using is not assigned the text I pass to \hbox, instead I gets empty box with zero width & height. Here is the code: \begin{tikzpicture}   \setbox37=\hbox{this is a text that I want to measure}   \node[draw] at (0,0) {text width is \the\wd37, text heigh is \the\ht37};   \node[draw] at (0,-1) {text contents is \box37}; \end{tikzpicture}  And here is the output:  What am I missing here?


I want to create a new database that I can use for testing, restoring it from a full backup from a production database. These backup file sizes are around 45,486KB, and the production database size is 3.7GB. When I try creating the new database, the default initial size (MB)says 45 for the Primary rows data and 3739 for the Log, Autogrowth by 5MB restricted to 50MB for the data and by 10 percent restricted to another large number!  Any advice on what is the ideal number to start with? When do I need to change them? I'm using SQL Server 2008. Thanks.

I have been monitoring file growth via the data collector in sql server 2008 r2 for two weeks. The database is growing consistently at around 35(MB)/Day. The DB has not yet hit the initial size of 2 GB.  The DB files auto growth is set to 5MB and I would like to try a different approach, so I am looking for suggestions and or comments.  There is a tuning task that runs every-week on Sunday night at 1:30 AM. The task will:    Check Database Integrity Shrink the Log File – (This is ok because logging mode is Simple) Shrink Database Reorganize Index Rebuild Index Update Statistics Clean Up History   I would like to add two more steps to the weekly tuning plan:   Grow the database file by 500 MB if the used space reaches a certain threshold or total size.   Grow the log file by 250 MB (after the shrink) if the used space reaches a certain threshold of total size.     By placing the growth burden in offline hours, I hope to gain performance by reducing the number of auto-growth events during heavy loads.  I have two questions relating to auto growing files.   The best place to put the file grow steps would be prior to the current steps or after?  If I use the ALTER DATABASE|MODIFY FILE to grow the file then how can I determine if SpaceUsedInFile >= (TotalFileSpace-@AllowanceThreshold)?


I want to apply text over image on hover to every picture without it messing up elements  container.  I've tried  and solutions similar, but It doesn't work for me.  This is what I have.   /*CSS*/ .item {   display: inline-block; }  img {   padding-right: 10px; }  .kulso {   text-align: center;   padding-top: 20px; }  .kulso2 {   text-align: center; }

Long Macchiato

Long Black

Café Latte

Ristretto

Capuccino

Flat White

Mocha Coffee

Affogato

   Demo site:   I understad I have to have a wrapper around each image and caption. My problem is, no matter what properties I'm modifying or adding while trying to apply the text over image on hover using , either...   "inline-block" is off, the pictures won't stay next to each other opacity, transition affects padding between pictures    the text is in the center of the page, not the picture the size of the pictures change   I noticed that adding
This is the text that appears on hover in the center of the image
 instantly messes up everything.  Please give me tips or solutions using my code I shared above!

I want to overlay one image with another using CSS. An example of this is the first image (the background if you like) will be a thumbnail link of a product, with the link opening a lightbox / popup showing a larger version of the image.   On top of this linked image I would like an image of a magnifying glass, to show people that the image can be clicked to enlarge it (apparently this isn't obvious without the magnifying glass).


Suppose that $(a,m,n)\in \mathbb{N}^{3}$, as $a>1$  How can I prove that $a^m-1|a^n-1 \Leftrightarrow m|n$?  I proved that $m|n \implies a^m-1|a^n-1$, but I couldn't prove the reciproque.

Let $a\ge 2$ be an integer. Show that for positive integers $m,n$, we have $a^n - 1$ divides $a^m - 1$ if and only if $n$ divides $m$.   I am having trouble showing this. I've seen a similar problem on here but it only shows one direction for the proof. I would like to see both directions.  This is what I have so far: Let $m = nq + r$, then $a^m - 1 = a^{nq + r}- 1 = a^{nq}a^r - 1 = a^{nq}a^r - a^r + a^r - 1 = a^r(a^{nq} - 1) + a^r - 1$. Since $0\le r\lt n$, $r = 0$ then $a^m - 1$ = $a^{nq} - 1$ so $a^m$ = $a^{nq}$ . Thus $m = nq$ hence $n\mid m$.


On subsurface I'm getting unexpected result like on     but I would like to receive result with smooth surface (not collapsed faces)  What could be wrong in my model ?

My problem is simple. I think that the strange deformations on the top are there because there are so many vertices in one face. How do I fix this while maintaining nice topology?  Although I triangulated the top polygon, the problem still persists.


Show that $2730\mid n^{13}-n,\;\;\forall n\in\mathbb{N}$   I tried, $2730=13\cdot5\cdot7\cdot3\cdot2$  We have $13\mid n^{13}-n$, by Fermat's Little Theorem.  We have $2\mid n^{13}-n$, by if $n$ even then $n^{13}-n$ too is even; if $n$ is odd $n^{13}-n$ is odd.  And the numbers $5$ and $7$, how to proceed?


I'm trying to use a package that imports color with the dvipsnames,usenames options. Unfortunately, my document uses the ACM format, which appears to already import the color package with no options.  The following file:  \documentclass[acmlarge,dvipsnames,usenames]{acmart} \usepackage{booktabs} % For formal tables \RequirePackage[dvipsnames,usenames]{color}  % Document starts \begin{document} % Title portion \title{A Multifrequency MAC Specially Designed for Wireless Sensor   Network Applications} \titlenote{We can add a note to the title}  \maketitle Body \end{document}   Gives the following, highly unhelpful error error:     LaTeX Error: Option clash for package color.   Is this a known problem? Is there an easy workaround for importing packages that conflict in their options?

What would happen when you load a package more than once, say via \usepackage{<package>} or \RequirePackage{<package>}.  For example:  \documentclass{book}  \usepackage{geometry} \usepackage{geometry}  \begin{document} test \end{document}   Will LaTeX ignore the double loading of geometry, or are there some problems and repercussions?


How to display custom columns' values in Content Query WebPart? Currently I have a Custom List with 3 columns Title, MobileNo and Address. Content Query WebPart Only Displays First Column's value (Title), but I want to display all column's values on CQWP. How to do it? What are my options?

Using SharePoint 2010, Having Custom List With 4 Columns, Now I am Using Content Query Web-part To Display List Data ,But Currently It Display Only First Column, SO How to Display Custom Fields in a SharePoint 2010 Content By Query Web Part


I am learning algebraic number theory, the exercises are so hard for me, could you please recommend me a book with answers? Many thanks!

I have studied some basic algebraic number theory, including Dedekind theory, valuation theory, and a little local fields. Now I am thinking to study more and deeper, and hoping to study class field theory, so please help me which book should I choose?  The teacher told me that I should read Lang's or Neukirch's, but I don't know which is better and to choose, or if there is a better one?  Thanks in advance.


I have a Macbook Pro and I search for files using Finder and Finder shows large previews of the first page of each file as I scroll through the list. I have not found that feature with Nemo or Nautilus on my Ubuntu desktop computer.   When I have to find files in a hurry I cannot afford to open them up one at a time to see if it might be the correct file.  Does Ubuntu have this feature or do I need to buy another Apple computer?

In the default file browser of Mac OS X, pressing space will preview the file in question.  Is there already something similar that I haven't found, or is there a way to add the functionality to Ubuntu?


Background. This question originates from the problem of finding a function $f$ such that its $n$-th iterate is equal to its $n$-th power, which I asked about . Now I would like to focus on the related case $n = -1$, because it seems to be quite a different problem. In other words, I am looking for a function $f$ such that its compositional inverse is equal to its multiplicative inverse, that is, $$f^{-1}(x) = \frac 1 {f(x)}.$$ It is immediate to see that this is equivalent to $$f \left ( \frac 1 {f(x)} \right ) = x$$ which is the equation in the title.    I believe I have found an example of a function $f \colon \mathbb Q^+ \to \mathbb Q^+$ satisfying the equation, but it is quite convoluted. The construction is as follows:  Let $x \in \mathbb Q^+$. Then we can write $$x = \left ( \frac {p_1^{a_1} \dotsb p_h^{a_h}} {q_1^{b_1} \dotsb q_k^{b_k}} \right )^n$$ where $p_1, \dotsc, p_h, q_1, \dotsc, q_k$ are distinct prime factors, $p_1^{a_1} \dotsb p_h^{a_h} \le q_1^{b_1} \dotsb q_k^{b_k}$, the exponents $a_1, \dotsc, a_h, b_1, \dotsc, b_k$ are coprime positive integers, and $n \in \mathbb Z$. Then we define $$\rho \colon \mathbb Q^+ \to \mathbb Q^+ \qquad \rho (x) = \frac {p_1^{a_1} \dotsb p_h^{a_h}} {q_1^{b_1} \dotsb q_k^{b_k}}.$$ Clearly the image $\rho(\mathbb Q^+)$ is countably infinite, so we can fix two sequences $(r_m)_{m \in \mathbb N}$ and $(s_m)_{m \in \mathbb N}$ such that: $$r_0, s_0, r_1, s_1, \dotsc, r_m, s_m, \dotsc$$ is an injective enumeration of $\rho(\mathbb Q^+)$.  Notice then that each $x \in \mathbb Q^+$ is either $r_m^n$ or $s_m^n$ for some $m \in \mathbb N$ and $n \in \mathbb Z$, in a unique way. Therefore, we define $$f(r_m^n) = s_m^n \qquad f(s_m^n) = r_m^{-n}$$ for all $m \in \mathbb N$ and $n \in \mathbb Z$. With this definition, we can check that the above property is satisfied: $$f \left ( \frac 1 {f(r_m^n)} \right ) = f \left ( \frac 1 {s_m^n} \right ) = f (s_m^{-n}) = r_m^n$$ $$f \left ( \frac 1 {f(s_m^n)} \right ) = f \left ( \frac 1 {r_m^{-n}} \right ) = f (r_m^n) = s_m^n.$$  My questions are:        Are there any less artificial functions satisfying the equation?   If so, is there such a function that is defined on an interval of $\mathbb R$?      Remark. If $f$ is defined on an interval $I$ of $\mathbb R$ and is always positive (or negative), then it is monotonic. Indeed, if $f$ were increasing we would have $$x_1 < x_2 \implies f(x_1) < f(x_2) \implies \frac 1 {f(x_1)} > \frac 1 {f(x_2)} \implies x_1 > x_2$$ and similarly if $f$ were decreasing.

Is there a function whose inverse is exactly the reciprocal of the function? That is $f^{-1} = \frac{1}{f}$.  We know that the inverse of a function is not necessarily equal to its reciprocal in general.


I downloaded a blender file and opened it but UI did not match V2.80.  I guess that because the file have been made in old version its UI did not match V2.80. I want change UI as V2.80 easily.  Is there any way for me?

Using blender 2.80 stable on Linux with openbox / nvidia. Once in a sudden the top menu with all my workspace was gone. Restarting blender does not help. Blender without the related file shows the menu. As soon the file is loaded it is gone. How can I get it back?


My cites are showing Surname, year as expected.. Except this one:  @article{wang2013genome,    title={Genome-wide transcript analysis of early maize leaf development reveals gene cohorts associated with the differentiation of C4 Kranz anatomy},    author={Wang, Peng and Kelly, Steven and Fouracre, Jim P. and Langdale, Jane A.},    journal={The Plant Journal},    volume={75},    number={4},    pages={656--670},    year={2013},    publisher={Wiley Online Library} }   That shows as "(P. Wang et al. 2013)" instead of "(Wang et al. 2013)".  I have noticed that if I change the name from Wang to Aang it correctly prints "(Aang et al. 2013)". But that's obviously not the correct name. What is happening and how can I fix it?  This is what I am using:  \usepackage[backend=biber,style=authoryear,bibstyle=authoryear,maxbibnames=99,maxcitenames=2,firstinits=true,uniquename=init,uniquelist=minyear]{biblatex}

I had been using bibtex and then biblatex for quite some time. For the newest edition of my book I moved to biber. I happened t notice that firstnames are sometimes generated and sometimes not. Has this been observed by others?   I have tried to make a minimal example but without success. Using the following code, which shows all the commands related to biblatex I have in my preamble I could not get the firstnames to be shown. Even with the stylefile I made for this book (second line) the error did not occur.  I have a dropbox with the latex files for the book available. I can give access to these.   What do you propose?  \documentclass[fontsize=10pt,twoside]{scrbook} \usepackage{hormonbuch} \usepackage[%   style=authoryear%   ,natbib=true%   ,sorting=nyt,backend=biber,doi=false,isbn=false,url=false]{biblatex} \addbibresource{../Literatur/EndokrinologieKundeNourl.bib}  \renewcommand*{\bibpagespunct}{\addcolon} \DeclareFieldFormat{pages}{#1}  \renewrobustcmd*{\enquote}{}  \renewbibmacro{in:}{%       Herbert Voss auf http://tex.stackexchange.com/questions/10682/suppress-in-biblatex   \ifentrytype{article}{}{%   \printtext{\bibstring{in}\intitlepunct}}}  \renewbibmacro*{journal+issuetitle}{%   \usebibmacro{journal}%   \setunit*{\addspace}%   \iffieldundef{series}     {}     {\newunit      \printfield{series}%      \setunit{\addspace}}%   \usebibmacro{volume+number+eid}% %  \setunit{\addspace}%   \newunit}  \renewbibmacro*{volume+number+eid}{%   \printfield{volume}% %  \setunit{\addcolon\space}%   }% % \renewbibmacro*{note+pages}{%   \printfield{pages}%   \newunit} % \begin{document}  \citet{CRT+88,FDe+85} \citep{CRT+88,FDe+85} \cite{CRT+88,FDe+85}  \printbibliography  \end{document}


Okay, so according to associative law: (A + B + C) = (A + B) + C So, could I also assume that ~(A + B + C) = ~A + ~B + ~C = ~(A + B) + ~C Where "~" means NOT and "+" means OR. Thank you very much.

The most relative that I found on Google for de morgan's 3 variable was: (ABC)' = A' + B' + C'.  I didn't find the answer for my question, therefore I'll ask here:  What is De-Morgan's theorem for (A + B + C)'?


Let's define $t_n$ by the recurrence $$t_0 = 1, \quad t_n = (-1)^n \, t_{\lfloor n/2\rfloor}.\tag1$$ It is easy to see that $|t_n|=1$, and the signs follow the same pattern as  the : $$1,\,-1,\,-1,\,1,\,-1,\,1,\,1,\,-1,\,-1,\,1,\,1,\,-1,\,1,\,-1,\,-1,\,1,\,...\tag2$$ (see  for an example of a non-recursive formula for $t_n$).  Now, define: $$\mathcal{S}(m, n)=\sum_{k=0}^{2^n-1}t_k\,k^m, \quad \color{gray}{m,\,n\in\mathbb{Z}^+.}\tag3$$ Computing some values of this sum immediately leads to the following conjecture:     $$\text{For all }\, n>m,\,\,\mathcal{S}(m, n)=0.\tag{$\diamond$}$$   (e.g. for $m=2$ and $n=3$ we have $0-1-4+9-16+25+36-49=0$).  How can we prove it? Is it a known result?

There is a question I have based on the fact: If you take a quadratic polynomial with integer coefficients, take the set $\{1,2,3,4,5,6,7,8\}$, make a partition $A=\{1,4,6,7\}$, $B=\{2,3,5,8\}$, and then evaluate the polynomial with the elements of each set you got an equality.  If now with a cubic polynomial and the set $\{1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16\}$, how to pick a suitable partition that accomplish the same fact? I mean is there a general formula for bigger degree?


here i am trying to validate the SVG image mime type. Even I am passing valid content-type also it fails. Can anyone suggest to me what's wrong with this regex?   const mimetypes = /image\/png|image\/jpeg|imagesvg+xml|image\/gif|image\/svg+xml/;  var result = mimetypes.test('image/svg+xml')  console.log(result)

I am tired of always trying to guess, if I should escape special characters like '()[]{}|' etc. when using many implementations of regexps.  It is different with, for example, Python, sed, grep, awk, Perl, rename, Apache, find and so on. Is there any rule set which tells when I should, and when I should not, escape special characters? Does it depend on the regexp type, like PCRE, POSIX or extended regexps?


// Using entrySet() to get the entry's of the map // m is previously created Map.  Set<Map.Entry<String,Integer>> s = m.entrySet(); for (Map.Entry<String, Integer> it: s) {      String str = it.getKey();  }   Map.Enty is just the interface.  An interface doesn't have the implementation of the method getKey();  why the code above works? Like how the compiler knows the behavior of getKey()?

In terms of Java, when someone asks:      what is polymorphism?   Would overloading or overriding be an acceptable answer?  I think there is a bit more to it than that.   IF you had a abstract base class that defined a method with no implementation, and you defined that method in the sub class, is that still overridding?  I think overloading is not the right answer for sure.


I have an integral with $\frac{1}{\tan^2x}$ needed to be evaluated. But instead of searching online for the antiderivative of $\cot^2x$, how would i find it from first principles?

How do you find the antiderivative of $\cot^2x$?  My steps to find it  First   $$ \csc^2 x = \cot^2 x+ 1 $$  because of Pythagorean Identities, so  $$ \cot^2 x= \csc^2 x-1$$ so $$ \int \cot^2 x\, \operatorname{d}x= \int \csc^2 x\, \operatorname{d}x - \int 1  \, \operatorname{d}x$$  simplying down to   $$\int \cot^2 x = -\cot x- x + C$$  because I know the derivative of $\cot x$ is $-\csc^2 x$.  I want to know if this is the correct solution because I have many gaps in my logic and frequently make errors and I started learning calculus a couple weeks ago.  If I got something wrong can you please tell me my mistakes.  Thanks, Bot


I'm developing C# VOIP LAN application. The application makes a call and shows the client is calling.  The problem is: After accepting the Call the following error message dialog box is shown.   The code which process the Accepted call is:  //Act according to the received message.             switch (msgReceived.cmdCommand)             {                 //We have an incoming call.                 case Command.Invite:                     {                                                     if (bIsCallActive == false)                         {                             //We have no active call.                              //Ask the user to accept the call or not.                             if (MessageBox.Show("Call coming from " + msgReceived.strName + ".\r\n\r\nAccept it?",                                 "VoiceChat", MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes)                             {                                 SendMessage(Command.OK, receivedFromEP);                                 vocoder = msgReceived.vocoder;                                 otherPartyEP = receivedFromEP;                                 otherPartyIP = (IPEndPoint)receivedFromEP;                                 InitializeCall();                             }                             else                             {                                 //The call is declined. Send a busy response.                                 SendMessage(Command.Busy, receivedFromEP);                             }                         }                         else                         {                             //We already have an existing call. Send a busy response.                             SendMessage(Command.Busy, receivedFromEP);                         }                         break;                     }                  //OK is received in response to an Invite.                 case Command.OK:                     {                                                     //Start a call.                         InitializeCall();                                                         break;                     }

I have a scenario. (Windows Forms, C#, .NET)   There is a main form which hosts some user control. The user control does some heavy data operation, such that if I directly call the UserControl_Load method the UI become nonresponsive for the duration for load method execution. To overcome this I load data on different thread (trying to change existing code as little as I can)   I used a background worker thread which will be loading the data and when done will notify the application that it has done its work.   Now came a real problem. All the UI (main form and its child usercontrols) was created on the primary main thread. In the LOAD method of the usercontrol I'm fetching data based on the values of some control (like textbox) on userControl.    The pseudocode would look like this:  CODE 1  UserContrl1_LoadDataMethod() {     if (textbox1.text == "MyName") // This gives exception     {         //Load data corresponding to "MyName".         //Populate a globale variable List<string> which will be binded to grid at some later stage.     } }   The Exception it gave was     Cross-thread operation not valid: Control accessed from a thread other than the thread it was created on.   To know more about this I did some googling and a suggestion came up like using the following code  CODE 2  UserContrl1_LoadDataMethod() {     if (InvokeRequired) // Line #1     {         this.Invoke(new MethodInvoker(UserContrl1_LoadDataMethod));         return;     }      if (textbox1.text == "MyName") // Now it wont give an exception     {     //Load data correspondin to "MyName"         //Populate a globale variable List<string> which will be binded to grid at some later stage     } }   BUT BUT BUT... it seems I'm back to square one. The Application again  become nonresponsive. It seems to be due to the execution of line #1 if condition. The loading task is again done by the parent thread and not the third that I spawned.  I don't know whether I perceived this right or wrong. I'm new to threading.  How do I resolve this and also what is the effect of execution of Line#1 if block?  The situation is this: I want to load data into a global variable based on the value of a control. I don't want to change the value of a control from the child thread. I'm not going to do it ever from a child thread.   So only accessing the value so that the corresponding data can be fetched from the database.


I know this question has been a billion times, but none of the answers are working (Google Chrome 61, Windows 10).    @font-face {   font-family: Antipasto;   src: url(Antipasto-ExtraBoldTrial.ttf); }  h2 {   font-family: Antipasto; }  p {   font-family: Antipasto; }  div {   display: inline; }
   <video width="30%" height="30%" controls>   <source src="video1.mp4" type="video/mp4">   No video. </video>

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     It works in the preview there, but not on my local computer.  Many of these answers are not working on my laptop either, I guess it's a graphics issue with Chrome.  Thanks for everybody for helping anyway.

I want to put two <div>s next to each other. The right <div> is about 200px; and the left <div> must fill up the rest of the screen width? How can I do this?


The site names and rep are not lined up correctly on the new top bar hamburger drop down:    Windows 7 Home Premium 64 bit, Firefox 56.0

In the sites dropdown, the reputation scores are misaligned:    This seems to happen only on Firefox (56.0), both on macOS (10.13) and Windows (7, 10) (thanks @Tom and @MonicaCellio). I've tested a couple of other browsers which do not have this problem. I've already cleared my cache.


Three friends brought 3 pens together each 10 dollars. Next day they got 5 dollars cash back so they shared each 1 dollar and donated 2 dollars. Now the pen cost for each guy will be 9 dollars (\$10 -\$1).  But if you add all 9+9+9 = 27 dollars and donated amount is 2 dollars so total 29 dollars.   Where is the other \$1?

I'm not sure how well known this "riddle" is but here it goes.  3 people go to a restaurant, each buy food worth 10.00.  When they're done, they give 30.00 to the waitress.  She gives the money to the manager, manager says they paid too much, gives 5.00 back to the waitress.  She comes back to the table, gives a dollar back to each person and then puts the remaining 2.00 in her pocket for tip.  So now, each person has paid 9.00.  9.00 x 3 = 27.00.  Plus the 2.00 in the waitresses pocket is 29.00.  What happened to the 30th dollar?  So what's the issue with this way of calculating (since if you backward it works fine), that doesn't give us the correct result?


i want to insert session cart into database mysql  here is my code  foreach($_SESSION['cart'] as $productid => $qty){     $query3 = "INSERT INTO dtransaction(trans_id, pro_id, quantity) VALUES ('$new', '$productid', '$qty')";     $query4 = mysqli_query($con, $query3);     print_r($query3."<br>"); }   the result of print_r  INSERT INTO dtransaction(trans_id, pro_id, quantity) VALUES ('TR033', '21', '1') INSERT INTO dtransaction(trans_id, pro_id, quantity) VALUES ('TR033', '16', '2') INSERT INTO dtransaction(trans_id, pro_id, quantity) VALUES ('TR033', '13', '8') INSERT INTO dtransaction(trans_id, pro_id, quantity) VALUES ('TR033', '12', '3')   im using auto_increament (int) for detail_id but in database, inserted like this  detail_id   trans_id    pro_id  quantity 197         TR034       21      1 201         TR035       21      1   detail_id jump 4, pro_id and quantity only insert the first data  what i want is like this  detail_id   trans_id    pro_id  quantity 198         TR034       21      1 199         TR034       16      2 200         TR034       13      8 201         TR034       12      3   how to do that? sorry for my bad english

I have a couple tables in which I created an object ID as either an Int or Bigint, and in both cases, they seem to autoincrement by 10 (ie, the first insert is object ID 1, the second is object ID 11, the third is object ID 21, etc).  Two questions:   Why does it do that? Is that a problem?


If you measure the cosmic background radiation you will find that in any direction it is roughly the same. However, if you were to travel near the speed of light relative to the Earth in a particular direction then the cosmic background radiation would be observed to have different values based on what direction you measure it from. So, does the cosmic background radiation imply a standard of rest in the universe?

It seems that we are . This is the speed of our galaxy relative to the cosmic microwave background. Where does this rest frame come from? Is this special in any way (i.e., an absolute frame)? EDIT: I think the more important question is "where does the CMB rest frame come from?".


I've written a script that uses ps -G <groupid> -o uid,cmd to log the commands that a certain group of the users of a system run in time. What I want to know is whether it's possible for the users to hide what they are doing from my script. And how can they do that if so. Please note that my users are not in sudo group. So they can't use prctl; I need another option that doesn't require administrative privileges I thought wrapping my code in a function and setting an alias for it and calling that alias would hide my script but it doesn't seem to work. So is there anyway to hide the code from ps? Here is an MVC of my code to show why I think the alias trick does not work: #!/bin/bash foo(){     sleep 3      ps -G 1,2,3 -o uid,cmd -H } alias bar='foo' while true do     sleep 1     ${BASH_ALIASES[bar]}     echo 1  done  And here is a summary of the related parts of what I get as the result: myid -bash                             (Reasonable) myid /bin/bash ./myscript.sh           (Reasonable) myid /bin/bash ./mysctipt.sh           (I don't care but I wonder why it's appearing twice!) myid ps -G 1,2,3 -o uid,cmd -H         (What I don't want to be viewable) myid sshd: myusername@pts/9            (Reasonable)  Please note that there was some indention in the output (due to -H option in ps) that I removed and the indentions of the duplicate line was different. From this I've concluded that making alias etc does not work. By does not work I mean that my users can't make alias for their commands and run those commands and hide their commands this way. Because if they could my ps command for which I had set an alias in my script shouldn't have appeared in the result. So here is the question in simple words: Is there anyway for the non-sudo users of my system to run some scripts in a way that I won't be able to notice using the ps command. p.s. Please note that I'm aware of the pam methods for logging and stuff. I just want to see if this method works. p.s.s. I pointed out the alias method because a friend told me this will work but it didn't. So I already explained that it doesn't seem to work to prevent people from coming and giving that as an answer. request!!! Can someone please explain to my why my question is closed as being an exact duplicate of another question while The answers in the mentioned question does not solve my problem at all!??

Using Ubuntu 12.04. is there any way to hide a running process ?  That process shouldn't' display in system monitor,top,htop . There is no problem to remember the process id (PID) so observation of the process can be done easily .but i want to hide the process completely . is there any way ?


how do i add or insert multiple rows in two columns, at the same time? i am trying this  insert into Gwish_bal(Account_code,Flag) values ( ('10192885','I'), ('10146883','I') );   and it is not working i keep getting ORA-00907: missing right parenthesis. i want to  insert a thousand numbers and flag them I. the output i need is a table which looks like this  a  ccount code    flag 800000008        I 800000009        I .... 800100000        I


I have this error when I run my batch "FATAL_ERROR System.LimitException: Too many SOQL queries: 201" even when changing the batch size to 10 ?! I know I need to remove the SOQL queries from the for loop, but I'm unsure how to get the same result otherwise.

This is a canonical question and answer developed by the community to help address common questions. If you've been directed here, or your question has been closed as a duplicate, please look through the resources here and use them to shape more specific questions. To browse all canonical questions and answers, navigate to the  tag. This question and answer is owned by the community! If you can improve it and make it more useful, you're welcome to edit it. I have a collection of records, like a List<sObject> or the Trigger.new context variable. I need to query other records that are related to these records either directly or indirectly, and I want to use the related data to make further updates. When I write a query in a loop, like for (Account a : Trigger.new) {     Account parent = [SELECT Name FROM Account WHERE Id = :a.ParentId];     // ... }  I keep hitting Salesforce query limits, and I know this is not best practice. What can I do to avoid this problem and bulkify my code?


I am new to Html & CSS. I want a heading which contains text like "Women safty". I want to warp the heading text with border. But when I apply border to text the border covers all the area in the width both left and right.I just want to add border around text only and the text needs to be in center.

I have a layout similar to:  <div>     <table>     </table> </div>   I would like for the div to only expand to as wide as my table becomes.


I'm installing a new USB printer HP LaserJet Pro M126Nw on a laptop. The printer is installed but when I print a document it's getting stopped.

Let's assume that one has some modern HP printer and/or scanner which is  supported by HPLIP package from official repository. Or supported by newer version of HPLIP package (see  about installation).  From official documentation () it is known that device needs proprietary/binary driver or plugin.  How should one install such plugin?


Im new to minecraft . I finally got into the nether and was disapointed. I could not find a nether fortress . Can i reset the nether? If i can please let me know. Im on Pc

I just opened a nether portal for the first time, and I must say, it's not a very good location, a sort of narrow trench/cavern thingy without any obvious clues as to which direction is "out".  I'm not willing to simply move my overworld portal (due to dilation it is unlikely to have much of an effect, anyway), and was wondering if there was a way to force minecraft to generate a new personal Hell for me to explore (hopefully one that doesn't involve me stuck in some wall!).


I saw this question on Stack Overflow: , and it made me wonder why badges are not "unawarded" like reputation when questions or answers are are changed or deleted.  Why are badges not unawarded when a question or answer's disposition changes?    There's a related un-answered/un-discussed question at . In the previous question, the authors makes a feature request to unaward them. This question asks why things are the way the are.

I was looking at a badge page, in particular the  one, and noticed that the first two users earning this badge answered to question which has been deleted afterwards.  I noticed that when this happens, I mean when a question is deleted, the reputation is restored: if a user gains 10 point of rep, for example, then he/she will lose them once the corresponding question is removed. The same happens if a user loses 10 points of rep: he/she will gain them again once the question is deleted.  Why this doesn't apply to badges?  I would expect that if the corresponding question is closed, one loses the earned badge ... or this logic applies only to revival badges since it can happen that a question of -5 score might be deleted?


I have a video surveillance system (a bunch of IP cameras, with private IPs) behind a router in a distant location. The only ISP that's available at that location has provided me with a 3G/4G USB dongle (so basically mobile Internet). Apparently this dongle (which connects to the router) does some routing/magic by itself (and is not configurable) so I can't use the router to do port forwarding (not in anyway that helps at least). This means that while the cameras have Internet access (so can push information to me), I can't access them directly over the Internet (so basically, no live feeds).  I'm thinking of getting around this by putting a low power computer (software doesn't really matter much in this question, but I'll use Linux) in the same subnet as the IP cameras - let's call this computer A; I also have a VPS rented somewhere that is publicly accessible via the Internet - let's call it B.  I think that this setup should allow me to work around the issue with my live feeds. At least conceptually if I get A to open a tunnel to B then via B I should have access to A's network.  Presuming the above works (I don't see why not, but .. that's why I'm asking) can you guys recommend a system that can accomplish the above with at little fuss as possible? I mean .. should I set-up a VPN with A as a VPN client and B as a VPN server; then anyone who wants to view the cameras simply connects to the VPN server installed on B?  I think this should work, but maybe there's an easier way than setting up VPN on every computer from where I want to check the cameras.  I'm not directly interested in the software (I'm sure that exists and I'll manage to configure it) but rather the networking concepts.   The ideal situation would be that I'd connect to B on (for example) port 8080 and that traffic will automatically be routed from B through a tunnel to A, at which point A will feed data obtained from camera "1" through that connection; then 8081 from camera "2" and so on.

I have a computer with CentOS (computer A) that configured as has an private ip 10.150.5.141 (with restricted firewall), can access internet and my ArchLinux VPS (computer B) with real ip w.x.y.z  How can I make another pc (computer C) that could access computer B to connect to computer A, but computer C cannot connect to computer A directly (because it's on A's own private network)?  I know that a tunnel can open local ports to another computer:port, but how to do the opposite?  I want to access computer A using ssh through computer B but computer B cannot access computer A, because the network on computer A is restrictive (can go out, but can't go in, because I have no access to their router)  I want something like this:  ssh -connect-to w.x.y.z:22 -open-port vvv -forward-to 10.150.5.141 -port 22   so that when I ssh w.x.y.z:vvv from computer C it will forwarded to private network 10.150.5.141:22.


I'm trying to deform a "chain" to follow a NURBS curve, but there's a weird inversion at the bottom of the loop.     I've tried various applies, scales, subdivisions, but the basic issue remains.  Thanks for any insights, I'm stumped.

I modelled a part of a bicycle chain added an Array and a Curve Modifier   everything worked nicely until I added cogs and translated and scaled the chain parts to fit the cogs.  I tried to apply transformations, re-added the Curve Modifier but had no success, it still deforms the chain that strange:    Before I messed it up it looked like this:    How could it be fixed?


I'm trying to gain a more conceptual understanding of derivatives and would appreciate your feedback on this.  Say I have a quantity, $x$, at time $t$. Now $x$ moves to a different location $x'$ in time $t'$ =  $t + \Delta t$.   Where I get confused is when we start talking about shrinking $\Delta t$ down to zero. I keep seeing people say that it represents an infinitesimal quantity, which confuses me even more. Similarly, people will say it "simply" represents a very small quantity.   I get that much but where I get lost is how small does $\Delta t$ have to be before we start treating it as $dt$ and not $\Delta t$?  In other words, is it correct to simply substitute numbers in to a quantity like $dt$? Could I say that at a certain instant in time, $dt$ = 4 seconds?   I've seen this done before in a few books and well, frankly it irritates me because I'm seeing the $d$ operator used in many different contexts. Some are saying you can substitute numbers in for something like $dt$ and others say no.

I have read the thread regarding , but it does not answer my question.  I am confused about the notation for change in Physics. In Mathematics, $\delta$ and $\Delta$ essentially refer to the same thing, i.e., change. This means that $\Delta x = x_1 - x_2 = \delta x$. The difference between $\delta$ and $d$ is also clear and distinct in differential calculus. We know that $\frac{dy}{dx}$ is always an operator and not a fraction, whereas $\frac{\delta y}{\delta x}$ is an infinitesimal change.   In Physics, however, the distinction is not as clear. Can anyone offer a clearer picture?


I've made my own texture pack/resource pack for Minecraft Java Is it possible to make it work for Minecraft windows 10, if so please help

I'm trying to use a texture pack designed for the Bedrock Edition of Minecraft, on Java Edition. I looked at the texture names for a Java Edition texture pack and compared those to the names of the Bedrock Edition texture names, and they aren't the same. A lot of the texture names are flipped, such as:   Jungle Log (Java = jungle_log.png) (Bedrock = log_jungle.png)   Most of the texture names are flipped, like the Jungle Log (and all of the other log types) and there are some .json files that are different and/or not there.  Trying to open the Bedrock texture pack would result in some animated blocks not being animated, other blocks play the wrong sound (or no sound) when broken, if OptiFine is in the mix, the skybox could be missing, which I am pretty sure would result in an always black sky, along with no sun and moon textures.  Any help in finding a program or site that can do this would be helpful, because I tried doing it manually, but almost every texture is different.  Any help is appreciated!


Is there a website where I can post my CV where potential academic employers can find me? To be more precise, I'm looking for postdoctoral position in the areas that uses differential geometry but could also use statistics, for example, computational neuroscience, computer vision, manifold learning etc.  P.S. this is my main question. But if you could answer the same question for industries for using the above topics and could access my CV online, that'd be well appreciated, because in case I don't get a postdoc, I'm keeping myself open to industry too.  Thanks in advance!

As I see faculty positions in Europe and North America is always based on applications. Is it common that a department head suggest a faculty position to a possible candidate?  I do not mean based on personal connection. Job websites (consider those devoted to academic jobs) encourage job seekers to upload their CVs.  Is it common that a department head search CVs uploaded on academic job websites and suggest a faculty possible to a job seeker?  Is there any success story? Does this system work in practice?


I need your help  I have this piece of code   interface A {       void PrintFields(); } class B : A {     int y;     void  A.PrintFields()     {          Console.WriteLine("y = {0}", y);     } }   and  I have this    interface A {       void PrintFields(); } class B : A {     int y;     public void PrintFields()     {          Console.WriteLine("y = {0}", y);     } }   }  so I am confused about the difference between those two different ways in implementing interface methods and why I can't use the public modifier in the first way.

What are the differences in implementing interfaces implicitly and explicitly in C#?  When should you use implicit and when should you use explicit?  Are there any pros and/or cons to one or the other?    Microsoft's official guidelines (from first edition ) states that using explicit implementations are not recommended, since it gives the code unexpected behaviour.  I think this guideline is very valid in a pre-IoC-time, when you don't pass things around as interfaces.  Could anyone touch on that aspect as well?


I recently switched from Ubuntu, and I was feeling very comfortable with using Ctrl + Alt + T to launch terminal. Can I assign Shift + Cmd + T to do the same thing in Yosemite? Specifically, I want a new terminal window to be opened.

I want to create a keyboard shortcut to i.e. open Firefox while I am working in another application. I know I can use ⌘ CMD+T when I am in Firefox to open a new tab.   I haven't found a way to create that kind of shortcuts in System Preferences.  Any ideas?


I am using classic asp/vbscript to load a RSS. In this case the URL should start with https rather than http so I get the error : Access is denied. How can I check if the target url is accessible and healthy and the use it?   Set xmlDOM = CreateObject("MSXML2.DOMDocument.6.0") xmlDOM.async = False xmlDOM.setProperty "ServerHTTPRequest", True xmlDOM.Load("http://iqna.ir/fa/rss/services/36")   I have tried to wrap it inside if/then but obviously will result in the same error:  if (xmlDOM.Load("http://iqna.ir/fa/rss/services/36")) then    'Proceess the RSS content end if

Is there a way to perform an HTTP GET request within a Visual Basic script?  I need to get the contents of the response from a particular URL for processing.


I am applying for Fall, 2015 in PhD programs (Computer science).   The admissions page of many universities I saw, demand an undergrad GPA of at least 3.0 and graduate GPA of at least 3.5  Now, I excelled in the two masters degrees I have (MBA, MS).  But I was an average student in undergrad. Average in India means that I scored around 68% in my undergrad years (I.T.)  If you ask me, I think this conversion thing is crazy. Many colleges in India grade/score very stringently, since the minimum percentage required to graduate is 50%. So, if I were an average student at an elite college in India, my CGPA/ Percentage would be 7.0 or 70%. Using this conversion table, my GPA on a 4 point scale would be 2.3.          In the US, however, you need a min. GPA of 2.75 to graduate. A GPA below 3 is considered to be a shocker, while a GPA between 3 and 3.5 would be considered below average. It'll never work; it's like comparing Apples with Oranges.  Am I missing something here? Any thoughts on how universities make this conversion?  Also, should I be using WES to ensure a "fair" reflection of my performance.

I'm trying to figure out the equivalence between grade schemes in different countries.  According to some Google results:   If you are a U.S. citizen, you need a GPA of 3.2+ (it varies, some say 3.2 and some others say 3.6, etc) to apply for a position in the UK (job or university) where the prerequisite is to have a minimum grade of 2:1. In UK 2:1 is earned if you have a 60-69% of the points. I've read that 2:1 is the same as 67%. In Spain we use a grading scheme of 10 points. So according to (2), for have a UK 2:1 you need to have 6-6.9 points. If you are Spanish and have 6.7, when converting it to GPA the result is 1.5.   However, if you take the above points and treat them as a math equation, the final result will be GPA 1.5 = GPA 3.2, which doesn't make any sense.  GPA 3.2 = UK 2:1 UK 2:1 = Spain 6.7 Spain 6.7 = GPA 1.5   Replacing now...  UK 2:1 = GPA 1.5     GPA 3.2 = GPA 1.5   My question is if someone has a better explanation on converting grades obtained in different countries.


How would the Magic Resistance trait interact with effects that impose disadvantage on saving throws (e.g. the sorcerer’s Heightened Spell  option, the first bullet point from the  spell description, several of the diseases caused by the  spell, etc.)? Would such effects remove the advantage on such saving throws granted by a creature's Magic Resistance trait? Or would they all be useless against it?

Many creatures in D&D 5e have a feature called Magic Resistance. One such is the :  Magic Resistance. The archmage has advantage on saving throws against spells and other magical effects.  So the Archmage has advantage on saving throws against magical effects. Suppose I wanted to weaken the Archmage's resistance to magic - I use some effect that gives disadvantage on the saving throw for my spell. Normally, this would balance out to a straight roll, as the  say:  If circumstances cause a roll to have both advantage and disadvantage, you are considered to have neither of them, and you roll one d20. This is true even if multiple circumstances impose disadvantage and only one grants advantage or vice versa. In such a situation, you have neither advantage nor disadvantage.  This seems to set a baseline for a straight roll on saves against magical effects, that the Archmage can never roll at disadvantage against magical effects. But is there a way to get around this? Keep in mind, such an ability must respect the  rule:  That said, many racial traits, class features, spells, magic items, monster abilities, and other game elements break the general rules in some way, creating an exception to how the rest of the game works. Remember this: If a specific rule contradicts a general rule, the specific rule wins.  The general rule here is that advantage and disadvantage balance out to a single die roll, so getting around Magic Resistance must either specifically override the rule for advantage and disadvantage, or eliminate Magic Resistance entirely. Is there any way (e.g. magic item, class feature, spell, etc.) to force a creature with Magic Resistance to make a save against a magical effect with disadvantage?  While writing this up I did find  which asks generally how to combat creatures with Magical Resistance, I intend this to be a (hopefully) more focused version of that question.


here is a set of data about core competency evaluation on public health of two age groups,the evaluation has 5 levels,so it's ordinal. and I'm tired of analyzing data with comparing their means.I'm wondering if there is a more advanced statistic methods to cope with these data?Many thanks!!!

I have some  gained from survey questions.  In my case they are  responses (Strongly Disagree-Disagree-Neutral-Agree-Strongly Agree).  In my data they are coded as 1-5.  I  don't think means would mean much here, so what basic summary statistics are considered usefull?


Homomorphic encryption is hyped by computer sciences because it offers great potentials. For example you can perform cloud based calculation while nobody gets to know you data.   I am wondering if there is any homomorphic encryption scheme that is CCA secure. Can't you always just choose a random message, encrypt it and link the ciphertext to the challenge? A decryption oracle will decrypt it without hesitation. As the attacker know one plaintext message, he can easily calculate the second one. By doing so he always wins the CCA experiment.

Is it possible to modify a homomorphic encryption scheme so that it can be CCA2 secure?  From the definition of a homomorphic scheme, it seems that it is malleable, which would result in lack of CCA2 security. So, if we use the regular method to convert a CPA secure scheme to CCA2 secure scheme (using a hash of the message and a random value), will it still preserve its homomorphic property? Please correct me if my understanding is wrong.


So yesterday I went ahead and bought the Samsung NP915S3G (ATIV Book 9 Lite) and installed Tahr in hope that everything would go smoothly. For the most part it; everything necessary seems to work off the bat. Unfortunately when I restart it, nothing boots. I erased Windows so that's obviously not an option, but the computer seems pretty dead certain that there's nothing there to boot. I think this might have a lot to do with UEFI which is a field I have next to no experience with. There also seems to be a fat32 partition that consistently reappears when I delete it.   Any help is much appreciated, thanks.

I have a Samsung Chronos 7 laptop (NP770Z5E) pre-installed with Windows 8, and I wanted to install Ubuntu 13.04 alongside it, so I can dual boot. Here is what I've done:  Updated BIOS to lastest version (P04ABU) using Samsung Updater Reduced Win8 partition by half, I left the others untouched Created a bootable USB stick using  and a Ubuntu 13.04 64-bit image Disabled FastStartup on Win 8 Disabled Fast BIOS Mode Boot Mode changed to CSM OS  Update:  Also disabled Secure Boot (I had to disable it in order to select CSM OS)  After that I saved the BIOS settings, and shut down the computer. I plugged in the USB drive, powered the computer on, entered the BIOS and tried to change the boot order. Oddly, there was only one option in the boot order screen, the USB drive (HDD didn't show up in the boot priority screen). I ignored that and installed Ubuntu. I've created 3 partitions from the unused spaced left: a 8GB swap, a 100MB BIOS boot partition, and the rest to ext4, mounted in /. Boot loader installed on /sda. After a reboot, this message appears:  All boot options are tried. Press <F4> key to recover with factory image using Recovery or any other keys for next boot loop iteration.  So I went to the BIOS to change the boot device priority, and the list is empty! Enabling Secure Boot and Fast BIOS had no effect. I used the Ubuntu Live USB to check the disk contents, I can see the Ubuntu and Win 8 partitions. I've used Boot Repair (using the Recommended Repair), with no avail, the Boot Repair log is here:  Boot Repair showed me a message about the system being a"EFI system". I suppose that means that I should have checked out the advanced settings. I don't know how to proceed. I don't know if it's a good idea to "recover with factory image" since I have modified the original partitions. Maybe I need to experiment with Boot Repair's advanced settings.


We are a couple from India and are spending 23 hours at Helsinki airport. Can we get a transit visa to leave the airport, see the city, stay at a hotel etc?

I found many related questions on this site but I am still not sure about the rules. How can I decide if I need a visa to transit? Schengen members as of May 2021 are as follows:  Austria Belgium Czech Republic Denmark (excluding Greenland and the Faroe Islands - but an open border with the Schengen Area is maintained) Estonia Finland France (excluding overseas departments and collectivities) Germany Greece Hungary Iceland Italy Latvia Liechtenstein Lithuania Luxembourg Malta Netherlands (excluding Aruba, Curaçao, Sint Maarten and the Caribbean Netherlands) Norway (excluding Svalbard) Poland Portugal Slovakia Slovenia Spain (except Ceuta and Melilla) Sweden Switzerland


Is there an easy way to verify that an object belongs to a given class? For example, I could do  if(a.getClass() = (new MyClass()).getClass()) {     //do something }   but this requires instantiating a new object on the fly each time, only to discard it. Is there a better way to check that "a" belongs to the class "MyClass"?

If class B and class C extend class A and I have an object of type B or C, how can I determine of which type it is an instance?


Given that $i,j,k$ are non-negative integers, how many possible ways can $i+j+k=n$ without taking the order into account?   In other words, what does the following sum equal? $$\sum_{i+j+k=n} 1$$  And then, for a generalized case of m numbers:  $$a_0+a_1+...+a_m=n$$  But the order for which i,j and k are placed does not matter, for example: $1+1+2$, $1+2+1$ and $2+1+1$ are the same combination.

I want to find out the number of possible combinations of $x$ numbers that sum to $y$. For example, I want to calculate all combination of 5 numbers, which their sum equals to 10.  An asymptotic approixmation is also useful. This question seems to be very close to number partitioning, with the difference that a number can be 0. See:    All possible partitions for sum 10 and 3 positions that can be zero, are 63 possiblities: (numbers shown as 3 digits)  019 028 037 046 055 064 073 082 091 109 118 127 136 145 154 163 172 181 190 208 217 226 235 244 253 262 271 280 307 316 325 334 343 352 361 370 406 415 424 433 442 451 460 505 514 523 532 541 550 604 613 622 631 640 703 712 721 730 802 811 820 901 910


I am looking for the average mass/energy density contained in the black hole per cubic  centimeter. As if the singularity did not exist.

How do scientists calculate that density? What data do they have to calculate that?


Let $T:\Omega\to\Omega$ a measurable function and $\mu,\nu$ $T$-ergodic measures on $\Omega$. I am trying to prove that $\mu\perp\nu$ (this is, they concentrate in disjoint sets).  My attempt was define $w=\mu+\nu$ and use Radon-Nikodým to obtain $f,g\in L^1(\Omega)$ such that $\mu\sim fdw,\ \nu\sim gdw$. Then I only have to show that $w(\{f,g>0\})=0$, but I couldn't progress much.  Note: for $\mu$ being ergodic I mean "$\mu$ is $T$-invariant and, for every measurable $A$, $\mu(A\triangle T^{-1}A)=0$ implies $\mu(A)\in\{0,1\}$.  Note2: I am not able to use the ergodic theorem.

Let $\mathbb P$ and $\mathbb Q $ different probability measures on $(\Omega, \cal F)$ and $T:\Omega \to \Omega$ a measurable function, which is $\mathbb P$ and $\mathbb Q$ ergodic.     Show $A \in \cal F$ exists, such that $\mathbb P(A)=1$ and $\mathbb Q(A)=0$.   Since $T$  is $\mathbb P$ and $\mathbb Q$ ergodic $\forall A \in \cal F$ with $A=T^{-1}(A)$, $\mathbb P(A) \in \{0,1\}$ and $\mathbb Q(A) \in \{0,1\}$. Furthermore I know since T is ergodic $\lim_{n\to\infty}\frac 1n \sum_{k=0}^{n-1}\mathbb P(A \cap T^{-k}(B))=\mathbb P(A)\mathbb P(B)$.  I was wondering if I can use this lemma here.   It exists some $ B \in \cal F$ such that $P (B) \ne Q (B)$. And I considered $A$ to be T-invariant, but still I can not lead this in the right direction.. Some help is highly appreciated!


Suppose $R$ is a commutative ring with identity of infinite cardinality. If for every non-zero  ideal $I$ of $R$ we have $|\frac{R}{I}|<\infty$ then $R$ is an integral domain. How do I go on proving this?

How can we show that if $R$ is an infinite commutative ring and $R/I$ is finite for every nonzero $I \unlhd R$, then $R$ is an integral domain?   I tried proceeding by contradiction: assume $a$,$b$ $\in R \backslash \{0\}$ and $ab=0$; then $R/(a)$ and $R/(b)$ must be finite, say $R/(a)=\{k_i + (a) : 1 \leq i \leq m\}$ and $R/(b)=\{l_j + (b) : 1 \leq j \leq n\}$. Does this mean $R$ must be finite? Or what about using the fact that $R/(a,b)$ finite?  Thanks for any help with this!


Does anyone know how to use apt links on Lubuntu with Opera? I've found tutorials that work on Opera Ubuntu and Firefox Lubuntu, but none for Opera Lubuntu.  Thanks

Opera web browser is not working with apt: links. Is there any solution for this problem? I downloaded this opera 32 bit deb from their website and my distro is Ubuntu 12.04.


Show using antiderivatives and using the binomial coefficient.

Other than the general inductive method,how could we show that $$\sum_{r=0}^n \frac{(-1)^r}{r+1}\binom{n}{r} = \frac1{n+1}$$  Apart from induction, I tried with  to check the validity, but I can't think of an easy (manual) alternative.  Please suggest an intuitive/easy method.


I had an external Mojave boot drive but the drive crashed and both Disk Utility's Restore and disk image mounter say the volume image I made a week ago is bad and can't be used despite having verified and mounted it immediately after creation. I badly need to get Mojave back so I can use my Winclone 7 license to restore the Windows boot partition that was on the internal drive I had upgraded to a higher capacity drive. I can't afford Winclone8 right now.

Sometimes it's hard to search for older versions of macOS & OS X  on the App Store.  This is an attempt to provide the canonical QA for this issue, as per the Meta QA -  I expect it to be modified over time to hopefully become a complete information resource.  How can I get any older version of a Mac OS to be able to run as a VM, or to reinstall on my Mac?


Similar to my earlier question I try to understand the characterization of topology by different approaches. There is the "classical" one with open sets, the one with closed sets, the neighborhood characterization and one with closure and interior operator, respectively. (In addition, there is also a possibility to define a topology with respect to filter convergence but I did not dig into that yet. Are there further approaches besides the ones mentioned?). Since $\mathrm{boundary}(A) = \mathrm{closure}(A)\setminus\mathrm{interior}(A)$ it should be possible to characterize a topology by a boundary operator only. My thoughts so far:  Theorem. Suppose that $\mathcal T\subseteq2^X$ is a family of sets and $\partial:2^X\rightarrow 2^X$. Then   $\mathcal T$ is a topology $\partial A := \mathrm{closure}(A)\setminus\mathrm{interior}(A)$   iff   $\partial$ satisfies   $\partial\partial A\subseteq\partial A$, $\partial(A\cup B)\subseteq\partial A\cup\partial B$, $A\subseteq B$ implies $\partial A\subseteq \partial B\cup B$, $\partial A = \partial(X\setminus A)$ and   $\mathcal T = \{U\subseteq\Omega : \partial U\cap U = \emptyset\}$.   I managed to show "$\Rightarrow$". I struggle with the reverse direction however. That $\emptyset,X\in\mathcal T$ is easy. But I could not manage to show the arbitrary unions and finite intersections. My attempt:  Let $A_i\in\mathcal T$ for $i\in I$, $I$ finite. Then  $$\partial\left(\bigcap_{i\in I}A_i\right) \cap \left(\bigcap_{i\in I}A_i\right) \subseteq \left(\bigcap_{i\in I}A_i\right)\cap(\partial A_i\cup A_i)$$ for each $i\in I$ by the third property. But Since $A_i\in\mathcal T$ it follows that $\partial A_i\cap A_i =\emptyset$. So we have $\partial\left(\bigcap_{i\in I}A_i\right) \cap \left(\bigcap_{i\in I}A_i\right) =\emptyset$. Is this correct?  Let $A_i\in\mathcal T$ now for all $i\in I$ with arbitrary $I$. Then $\emptyset = A_i\cap\partial A_i$ for all $i$ by assumption. Thus, $$\begin{align*}\emptyset &= \bigcup_{i\in I}(A_i\cap\partial A_i)\\&=\bigcup_{i\in I}(A_i\cap\partial A_i)\cap\partial\left(\bigcup_{i\in I}A_i\right)\\&\supseteq\bigcup_{i\in I}A_i\cap\partial\left(\bigcup_{i\in I}A_i\right)\end{align*}$$ because intersection with emptyset is emptyset. So, $\bigcup_{i\in I}A_i\in\mathcal T$.  Note In the other questions for which my question was flagged as duplicate answer this questions by showing that there exists a one-to-one relation between boundary and closure. I however wanted to prove that boundary characterizes a topology straight.

The axioms of a topological space are usually stated in the "open set" form: A topological space $X$ has a set of subsets $\tau$ whose members satisfy:   $\emptyset$ and $X$ are in $\tau$. $\tau$ is closed under arbitrary unions. $\tau$ is closed under finite intersections.   We will call this the usual open set axiomatization of a topological space. The open set axiomatization is probably the most economical, but of course there are other ways as well, such as the  which axiomatizes the topology using the closure operator.   In his note , Pete L. Clark gives several alternative characterizations of a topology, most of which have details given. It was mentioned, I think originally by Willard, that it is "possible, but unrewarding to characterize a topology completely by its [boundary]". I could find no further references on this, and I am wondering how it might be done (unrewarding as it may be).  So my question is this: How can a topological space by axiomatized using the boundary operation as the primitive notion? A complete answer should give a list of axioms required for the formulation, as well as a sketch of how they are equivalent to the usual open set formulation.


Basically what I have is a very tricky situation. I have ubuntu alongside windows 8.1 as a dual boot. My win 8.1 have recently got into some problems and I cannot access safe mode neither windows repair works. Now I have an idea to insert win 8.1 dvd to repair my old windows but cannot boot because of a ubuntu gnu grub. What is the best way to boot windows from gnu grub because I tried to make it work using bios which also didn't work ?

I installed Windows on my computer, followed by an installation of Ubuntu. However, now I'm unable to boot into my Windows install.  What can I do to fix this?