I am recently reading a book called "Small Steps". So there is one sentence I just came across, which was "If he tried to take too big a step,...", I thought this sentence was grammatically wrong, but if it is, the author will not have written it. Right?  Please tell me why "too big a step", or simply "too (adj.) a (noun)" is correct and how to form a sentence like this, I would like to try using new phrases in my essays.  Thank you very much! xx

You're too clever a man to imagine this.   The above sentence was , a man of excellent rhetorical skills.   Since he said it, I doubt it's wrong, grammatically. But, I wonder if there is an explanation for this. Because adjectives always come after the article not before it. e.g. You're a clever man.   How could this be, grammatically?


On I2C buses you can hock up 112 devices. So why do so many microcontrollers have up to four I2C ports, when you could just operate enough devices for most applications on one I2C interface?

The I²C protocol allows, in theory and with 7-bit addressing, up to 127 devices to be connected to the master. This is a large number, so why would any low-cost microcontroller (e.g. ), have more than one I²C port? Why is it needed?


I want to set the multiple values in lookup column. my string format is id#;id#;id#; but it is giving error.

I want to add values to a lookupmulti field with c#. the form shows the field correctly but my code just won't work:  SPList list = SPContext.Current.Web.Lists["testlist"]; SPListItem item = list.GetItemById(someId); SPFieldLookupValueCollection fieldValues = new SPFieldLookupValueCollection(); foreach(int id in itemIds) {    fieldValues.Add(new SPFieldLookupValue {LookupId = id}); } item["lookupmultifield"] = fieldValues;   The code above is not exactly my code, but it's how i thought it should work.  FieldValues has 2 entries, but only the first is inserted in the lookupmulti field. can anyone help?


I've been looking through the literature because I want to see if anyone has implemented this idea I have. I know data compression algorithms work by removing redundancy in data. I was wondering though if this scheme I have would work.   Ordinarily the idea of a hashing function $H$ is designed so that $H(x)$ (where $x$ is the message) is easy to compute in the forward direction, but difficult to compute in the reverse direction (computing $H^{-1}(x)$ is intractable). But I also notice another thing about $H$. In practice the length of $H(x)$ is can be as large as 512 bits (I'm referring to the SHA-512 hash). This means that $H$ can map $2^{512} \approx 1.34 \times 10^{154}$ hashes to theoretically an infinite number of pieces of data. It's just that in practice the message space of all possible messages are not necessarily messages that have any meaning to humans. The number of total human readable messages may be on the order of say $2^{520}$ (meaning the total number of unique messages in the entire history of mankind).  So now let us suppose we have a hashing function $h$ which is easy to compute in both directions. We could compress our large data file $D$ into a short hash $h(D)$ that maps to $D$ and several other unintelligible "messages." So now to transmit $D$ all we have to do is to transmit $h(D)$ (which is short) and then the receiver would reverse $h(D)$ until they find a possible intelligent message and they could reconstruct $D$. If such a thing could work it would be possible to compress large amounts of data into short messages.  Does anyone know if such a thing has been done before?

So, I was having this weird thought. If the checksums(MD5 or SHA...) are unique to any file and are modified if any part of the file is edited, why cant the checksums be decoded back to get the original file? That is if I want to send a large(say 700MB) video, instead I could send just the hash and the file be decoded locally in my friend's computer. I know the thought is stupid, but is it possible by any chance? Or am I missing some thing here? And forgive me if I'm wrong, I ain't a professional.


My If/else statements are not working in my while loop. The purpous of this program is "for the user to enter a number, print every number leading up to it, tell if the number is even or odd, print the sum. And then have the user enter if he wants to repeat the process or not" Here is the source code (Keep in mind that I am a student and very new to coding):  print("Christian Dooley") print("Lab #5") import sys  def calculation():  counter = 0  NumberOfElements = 1  numbers = []  sum = (0)  for i in range(NumberOfElements):      value=eval(input("Enter a new number:"))      numbers.append(value)  while counter <= value:      print(counter)      sum+=counter      counter+=1      if counter % 2 != 0:          print("This number is even")      else:          print("This number is odd")  print(sum)  while True:  calculation()  repeat = input("Do you want to 'count' another number \n Awnser yes or no: ")  if repeat == "Yes" or "yes":       calculation()  elif repeat == str("no") or str("No"):       break   This is the part of the code that is giving me trouble:  if repeat == "Yes" or "yes":           calculation()      elif repeat == str("no") or str("No"):           break   The if statement will keep running over and over, no matter what I enter for the repeat variable, can anyone tell me why.

When using IF statements in Python, you have to do the following to make the "cascade" work correctly.  if job == "mechanic" or job == "tech":         print "awesome" elif job == "tool" or job == "rock":         print "dolt"   Is there a way to make Python accept multiple values when checking for "equals to"? For example,  if job == "mechanic" or "tech":     print "awesome" elif job == "tool" or "rock":     print "dolt"


If yes why is it the case that it have this property? There must be some mathematical proof or intuitive understanding in that case.

For a nonnegative random variable $X$, how to prove that $E(X^n)^{\frac1n}$ is nondecreasing  in $n$?


I have a file  content like below  cat file  Hello How are you ? I am good Watsapppp bla bla    But When I am exporting and echoing its value/content , This gives everything in same line and bit different.  export filename=$(cat file)  echo $filename Hello How are you 0 1 2 3 a m p q I am good Watsapppp bla bla   My Requirement in script is to print same content as in file.  Should be  $filename Hello How are you ? I am good Watsapppp bla bla   I mean when I pass the value of $filename , it should print above content

list=`ls -a R*` echo $list   Inside a shell script, this echo command will list all the files from current directory starting with R, but in one line. How can I print each item on one line?  I need a generic command for all the scenarios happening with ls, du, find -type -d, etc.


'  #include <stdio.h> #include <math.h>  int main(){           int i;           float num = 4.700;            for(i=1;i<5;i++){                printf("%0.3f\tx%d\t\t=%d\n",num,(int)pow(10,i),(int)(num*pow(10,i)));         }           return 0; }   ' This code prints the following to the console: '    4.7000   x10        =46   4.7000   x100       =469   4.7000   x1000      =4699   4.7000   x10000     =46999   ' This result is not consistent with all floating point values    1.2000 prints out ...120...1200 etc 1.8000 is strange again  I am working in Codeblocks and my question is why do some floats react this way?I there something fundamental to C or the mingw compiler that I am missing? Or is there something wrong with my code? Thanks for the help and sorry if it's a repeat question

Consider the following code:   0.1 + 0.2 == 0.3  ->  false   0.1 + 0.2         ->  0.30000000000000004   Why do these inaccuracies happen?


I am trying to use the Blender cycles standalone plugin with the xna app to render scene. But I am stuck as I don't know the structure of the camera matrix. In xna view matrix structure is  . Can somebody explain the same for  Blender?

As asked.   I need a way to get the projection matrix of the active camera, via python.  EDIT: I think this question is different from the one asked , because getting a matrix is different from setting the matrix.  Although, since this question was so quickly marked a duplicate, I guess the answer is the same.


I have a div block that simulates a small spinner, everything works fine however with the css configurations that I have it is positioned in the upper right wing, I tried to center it but when I see it from a mobile device it moves from place .. how could to center it without it changing position in devices with different sizes?  .spinner {   display: block;   position: fixed;   z-index: 1031;   top: 15px;   right: 15px; }

Best way to center a <div> element on a page both vertically and horizontally?  I know that margin-left: auto; margin-right: auto; will center on the horizontal, but what is the best way to do it vertically, too?


I am trying to construct a model for single-label multiclass classification using Keras in a Jupyter notebook. Here's my model (or see ):  model = models.Sequential()  model.add(layers.Dense(8, activation='relu', input_dim=9)) model.add(layers.Dense(8, activation='relu')) model.add(layers.Dense(4, activation='softmax'))  model.compile(optimizer='rmsprop',               loss='categorical_crossentropy',               metrics=['accuracy'])  hist = model.fit(X_train, y_train, epochs=20, batch_size=256, validation_split=0.2, shuffle=True)   I'm getting training accuracy of 0.8538, a validation accuracy of 0.8533, and a test accuracy of 0.8524. However, these values don't change for any of the following:   adding/removing hidden layers increasing or decreasing the width of each layer (even to 1) changing the optimizer to adam changing softmax to sigmoid (!) changing batch_size validation_split of 0.1 and 0.2   Also, these values are reached within 1 epoch and don't budge from there. My losses do similar at ~0.57. I'd expect after a lot of epochs to see some level of overfitting, but I'm just getting training and validation loss flat-lining at slightly different values.  I've tried   normalising the data filling missing values   I feel there must be something seriously broken with my workflow but can't for the life of me figure out what.  EDITS   there are 271116 data points, 1/3 of which are used as test data as per Sycorax's suggestion, I reduced learning rate. This just slowed the process of arriving at the same values

I'm training a neural network but the training loss doesn't decrease. How can I fix this?  I'm not asking about overfitting or regularization. I'm asking about how to solve the problem where my network's performance doesn't improve on the training set.    This question is intentionally general so that other questions about how to train a neural network can be closed as a duplicate of this one, with the attitude that "if you give a man a fish you feed him for a day, but if you teach a man to fish, you can feed him for the rest of his life." See this Meta thread for a discussion:   If your neural network does not generalize well, see:


When i  am tying to take user input in python then it is taking input in next line but I want ti to take input in same line. How to achieve that?   I am taking input like this  print("Enter your name:",end=" ")   It is showing on console as  Enter your name: Ankit   but I want it as  Enter your name:Ankit

I'd like to do it in Python. What I'd like to do in this example in C: #include <stdio.h>  int main() {     int i;     for (i=0; i<10; i++) printf(".");     return 0; }  Output: ..........  In Python: >>> for i in range(10): print('.') . . . . . . . . . . >>> print('.', '.', '.', '.', '.', '.', '.', '.', '.', '.') . . . . . . . . . .  In Python print will add a \n or space, how can I avoid that? Now, it's just an example, don't tell me I can first build a string then print it. I'd like to know how to "append" strings to stdout.


I have already read a bunch of threads and haven't gotten anywhere. I installed Ubuntu command-line only, then installed the Gnome desktop environment separately.  Upon booting the desktop, the proper resolution appeared. I went to Software & Updates >> Additional drivers, then switched to the recommended "Using NVIDIA driver metapackage from nividia-driver-430 (proprietary, tested)". I hit Apply Changes, then rebooted the machine once finished.  The resolution broke. I tried reverting to the original "Using X.Org X Server - Nouveau display driver from xserver-xorg-video-nouveau (open source)". No dice. The resolution remained at 1024x768.  After reading through the xorg.0.conf log it appears the monitor is not recognized, which is causing the problem.   xrandr output:  $ xrandr: Failed to get size of gamma for output default Screen 0: minimum 1024 x 768, current 1024 x 768, maximum 1024 x 768 default connected primary 1024x768+)+) 0mm x 0mm    1024x768 76.00*   There is no x11/xorg.conf.d file. Output of X -configure  X -configure _XSERVTransSocketUNIXCreateListener: ...SocketCreateListener() failed _XSERVTransMakeAllCOTSServerListeners: server already running (EE) Fatal server error: (EE) Cannot establish any listening sockets - Make sure an X server isn't already running(EE) (EE) Please consult the The X.Org Foundation support          at http://wiki.x.org  for help. (EE) Please also check the log file at "/var/log/Xorg.0.log" for additional information. (EE) (EE) Server terminated with error (1). Closing log file.   Any ideas?

After installing Ubuntu 10.04 with my Samsung SyncMaster B2030, native resolution (1600X900) is not found in the list of resolutions.


Ok so I installed Ubuntu dual boot with Windows 7 last year. But I found out I never used it so I decided to wipe the Ubuntu drive from Windows. Next startup I got this error, note the grub partition has been wiped and I have no way to booting into Win 7 now cuz of this grub rescue error. I have a Kali Linux live USB, so I can boot and do some changes (although this is technically not a Ubuntu live USB)  Edit: I can't boot into neither Windows or Ubuntu (It's deleted) now, so commands to run in Ubuntu won't work for me. And btw the grub files are gone.  Any idea how to fix this? Thanks :)

I have absolutely no experience with Linux, and I desperately need to get my computer back up and running again with Windows.  How do I remove Ubuntu and reinstall Windows?    Editor's note: many of the answers are about removing Ubuntu from dual-boot but keeping Windows (which is a bit complicated), while other answers are about removing Ubuntu from single-boot (which is easy: basically just format the disk while installing Windows). The question as written is ambiguous between dual-boot or single-boot.


I don't know if this is possible in Minecraft, but I will ask. I want if someone says "Shop" in certain coordiantes (Example: 985 53 1100 to 1107 53 978), he will teleport to 1046 54 1128.  How can I do this?

I want to be able to detect if a certain word in chat is said like: Console: Please say yes to be teleported or no to remain Player1: yes Player1 teleported to [insert random coordinates here]  Something that would monitor the chat for a certain word.


This is the RAID0 structure:    there have 3 disks,  I have a question about this, when write data into disk, is it write disk A full, then write disk B?   or is write a little data into disk A, then write into disk B a little, then write to disk C a little?

This is a  about RAID levels.    What are:   the RAID levels typically used (including the RAID-Z family)?  deployments are they commonly found in? benefits and pitfalls of each?


I am under Ubuntu 14.04 with Gnome Classic as desktop environment.  I have a process, whose status is Sl, see below:  $ ps  aux | grep PDFXC t        20363  0.1  0.0 2676268 6436 pts/61   Sl    2015  13:03 /home/t/programs/PDFXCview.exe bash4.3.pdf                                         What does Sl mean?  I don't remember whether I have tried to kill it by right clicking and selecting "close". Maybe or maybe not. But now I can't find the window for the process in the desktop environment's panel. Is it still possible to find its window, and make it to the front of the desktop environment?

I'm trying to find a way to raise all the windows that have one, specific title.  For example, I have two windows named superconky (yes, you guessed it, I'm trying to get conky running in lubuntu).  I have a command I got from the LXDE forums: sh -c 'wmctrl -k on; wmctrl -a superconky;'  I use it to show the desktop, except conky. It works perfectly, but only if you have one conky. If you have two or more, you get left with one and all the others minimized.  So, what should I do to raise all the windows?  Thanks in advance.


The unofficial social convention in the US seems to be that everyone tips 15-20% on their food and in exchange very good service is expected, compared to other countries. But what if I didn't like the service? How bad does the service have to be to justifiably leave no tip at all?

In Aus/NZ you don't tip, it's not generally part of the culture.  In the US/Canada you seem to tip for almost everything, but it's meant to be for a good job.  However I've also found some workers have the tips factored into their pay - ie if you don't tip them, they're getting less than minimum wage.  Therefore, should you still tip in these countries when the service is appalling?


Here singing is a noun:   I like singing.   But what about here?   I like singing loudly.   Loudly is still an adverb, right? But singing is still  behaving like a noun, right?   So which is it, a noun or a verb? How can it behave like a noun when it gets modiﬁed by an adverb?

I know that a gerund is a noun, so it should be modified by an adjective. However, it is also a verb form. Can I modify it by using an adverb?


Where in the UK can I change Kazakstan money, I recently travelled back and did not get time in Almaty airport, and the currency people at the airport would not change the money I have?

I've just returned from several unusual countries in Asia, and annoyingly despite being told I'd have no problem, I'm unable to find anyone in London to change back to pounds.  I've tried Travelex in Heathrow, a currency exchange place, and the post office.  The currencies include cash from: Mongolia, Kyrgyzstan, Kazakhstan and Uzbekistan.  Most of the responses when shown the money is to the tone of "What the hell currency is this?" which doesn't fill me with confidence.  Any suggestions welcomed for places that may change this. Otherwise I may need to go back next year ;)


$ find '/media/andy/MAXTOR_SDB1/Ubuntu_Mate_18.04/'* -mtime +5 {} \; find: paths must precede expression: `{}'

while running find command to find all the jpg files in the current directory as   find . -maxdepth 1 -type f -name *.jpg   i am getting the error as :   find: paths must precede expression: pic1 (1).jpg  Usage: find [-H] [-L] [-P] [-Olevel] [-Dhelp|tree|search|stat|rates|opt|exec] [path...] [expression]   i am not able to figure out what is wrong with that .


I would like to have a tilde like this: ~some text  But it seems hard / impossible to easily achieve that in LaTeX.  Is it possible to have a "vertically centred" tilde which also looks like a "normal" tilde and is represented by that character so it is possible to search for it in the text? Additionally I wanted to know why this seems so hard to achieve in LaTeX as that would help me understand the philosophy and mindset of LaTeX and to use it better and more efficiently. My current effort looks like this but the tilde given by \textsuperscript{\texttildelow} is vertically too high. the nation's \texttildelow $\sim$ \textasciitilde \textsuperscript{\texttildelow} 2,500 high complexity

How do I set the tilde (~) character correctly in LaTeX?  There’s a  on Stack Overflow, with a lot of answers. But dare I say it? They all suck:   \textasciitilde is too high, \texttildelow is too low. $\sim$ can be tweaked to look more or less acceptable: {\raise.17ex\hbox{$\scriptstyle\sim$}} – but even that is a hack and uses the wrong symbol.   The point is – the tilde character is definitely an existing glyph in any font I am tempted to use. How can I just access and typeset that character, please? Without resorting to some other, similar-looking glyph that first needs to be nudged into place using a cunning combination of font size and raised boxes?  There must be a possibility to access that glyph directly from the font definition.  To demonstrate, look at this screenshot which attempts simply to display a C++ destructor of a type T (~T):    Compare this with the symbol we get in the browser: ~ – that’s what I want.


I have LinkedList of generic Date  LinkedList<Date> dateList = new LinkedList<Date>();`         try         {         a= sdf.parse("21/03/2000");         b= sdf.parse("21/03/2006");         c= sdf.parse("18/09/2008");         }catch(ParseException pe)         {             System.out.println("not a date formate");         }         dateList.add(a);         dateList.add(b);         dateList.add(c);   if a user enters a date i.e 12/05/2002, so the user should get a prompt that the entered date is between 21/03/2000 and 21/03/2006 and also it should give the answer that "the given date is coming after 21/03/2000".  I tried sorting. but didn't work. new to Date class.

I have a list of Date objects, and a target Date. I want to find the date in the list that's nearest to the target date, but only dates that are before the target date.  Example: 2008-10-1 2008-10-2 2008-10-4  With a target date of 2008-10-3, I want to get 2008-10-2  What is the best way to do it?


So for months, I have been struggling to live with a 128 GB SSD. The available space of the drive is getting smaller and I had to uninstall some programs over time.  I currently have this SSD as my C drive and a 2TB HDD as my second drive where I try to save everything less important.   I am planning on getting a 250GB or even 500 GB SSD. I then would like to move my current Windows 10 image over to the bigger SSD and use the old one as a dual boot drive for Ubuntu.   Is this feasible? And if, how would one proceed in doing this?

Is there a free way to clone a full Windows 7 installation from HDD to SSD? (The free part is important, I know I can pay for Acronis True Image.)      SSDs are usually much smaller than HDDs which complicates matters. For instance, I have about 50GB data, my new SSD is 80GB but I still can't use Windows clone/restore system if my HDD is something like 300GB.  Therefore, I'm looking for a third party tool that will be able to:   Create a clone of my C: partition Store it onto an external USB drive Boot from some rescue / restore CD Load the image onto the new SSD   Acronis True Image seems like a tool that should support this but it's a paid-for software and the trial version cannot create clones. Acronis Migrate Easy is a fully functional tria for 15 days but need both the HDD and SSD connected at the same time which is a bit of a problem for me as a laptop user.  P.S. I almost got there combining Windows image backup combined with Acronis True Image restore CD (which can load .vhd's) but was not able to boot as some boot information were probably lost and could not be repaired using the Win7 installation DVD.


I have 2 categorically dependent variables(both binomial) in logistic regression which individually both give positive estimates against the response(binomial). However if modeled together one give positive and other give negative. I checked for the multicollinearity using VIF, which seems fine. What could be the possible reason for such behaviour.

In my logistic regression the sign of coefficients of a variable (location distance of an amenity) changes based on other variables (with time -ve, with travel distance +ve) in the model. When the location distance is the only variable in the model, it has +ve sign.    Should the variable need to maintain the +ve sign no matter what other variables are added in the model? Does changing sign signify a multicollinearity issue? Some IVs are gaining significance while in a bivariate model, they didn't show significance and vice versa. Is it okay to add variables that don't have much significance (ex: travel distance has a significance of 0.33 individually, but 0.05 when added with other variables) but becomes significant in the model? thanks.


How does one simply (and quickly) provide feedback that an answer was helpful or vote UP on Stack Overflow without first establishing a reputation? I don't care about point games, but would still like to thank someone for their excellent answer, and subsequently saving me a bunch of time.  I'm fairly certain I'm asking this Stack Overflow-related question in the wrong place. I tried the tags meta.stackoverflow.com, getting started, and reputation, but they don't exist and can't be established without points.    Do I have to ask questions before I have the authorization to give any feedback?

I think more reputation points should be required to add a new answer than to upvote an existing answer.  I don't continually watch for new questions, so usually when I find a question it has already been answered.  It seems bit inappropriate to answer an already-answered question in order to contribute to the conversation, but until you earn reputation, you can't upvote or comment; you can only add new answers, which prevents me from contributing at the moment as much as I would like to.  This seems backwards to me. If someone incorrectly upvotes a bad answer, the damage is minimal, as other users can down vote it and upvote the correct answers. On the other hand, an incorrect answer wastes the time of everyone who reads it.  So, IMHO, it should require more reputation points to add an answer than to upvote or comment on an existing answer.  I wouldn't say say that users should be prevented from answering unanswered questions until they have x reputation points, as that might prevent users who have answers from providing them, but perhaps it should be required if the question is already answered, to discourage users from reiterating previously given answers.  What do you think?


I know the peel on the cloves of garlic are edible, but what abput the papery skin on the outside covering all of it? I feel dumb for asking this but is there a difference? The post/question in the following link got answers about the peel, and not skin/paper on the outside. Again, sorry if this is redundant.

I ask NOT about the white outer layers that must be peeled and I do peel. But I lack the time to peel the red peel off cloves. Is it safe to eat?


A random variable $X$ has the PDF  $$f_X(x)=\begin{cases}   Cx^2 & -1\le x\le 2,\\   0 & \text{otherwise},   \end{cases}$$ and  $Y=X^2$ . Calculate $E(Y)$.

A random variable $X$  follows the distribution $$f_X(x)=\begin{cases}   Cx^2 & -1\le x\le 2,\\   0 & \text{otherwise},   \end{cases}$$ and  $Y=X^2$ . Calculate $P(X ≥ 0)$ can some one give me any hint to solve this question.


I fly a lot, but never accept a mobile boarding pass as I need a decent signal to display it. My iPad allows me to save screenshots to the gallery. I find it incredibly usefull, but can't find it on my Nexus 4!!

Is there a way to take a screenshot of an Android device and save it as an image file?


I am just a beginner in Blender, When I am editing an object on the plane, the 3D Viewport is not showing the accurate direction and path, due to which I am unable to do editing easily on that object. I tried to focus the camera on the viewport, but it wasn't helpful.How should I correct the angle of the camera?

Often I want to just point the camera to an object or a specific area in my scene to get an idea of how it'll look in the render. What's the most painless hassle-free way to do this in blender?  A quick search on the blender wiki does not lend itself to easy look-up due to all the noise in the search result.  This question could probably be broken down into these two main questions:   How do I point a selected camera to the current 3d-cursor location in the scene? How do I point the selected camera to the currently selected object(s) in the scene?


Votes count is split into two strings.    Link for question:   List of defaultly installed fonts in my phone:   The bug does not affect 2 of 6 fonts (independently of font size):    NewSmartGothic Coffee      App Version: 1.0.85 Device Manufacturer: LGE Device Model: LG-D802 OS Version: 5.0.2 (152331922a212)

UPDATE: It turned out to be the Ubuntu font I had applied. I went to the system font and it comes out normal. However, I personally think it would make sense to count the dash as a character and resize the text as if it were three numbers, like the high upvotes.  I guess this question should be closed as non-reproducible, if that's a reason on meta.se.     has the same subject, but the comments say it's been fixed. I am not using the SE app from 2013, but rather the newest version 1.0.85 and since it doesn't happen to others, I assume it's something with my screen size. I also don't see this with positive three character vote counts at all, so it's not really the same thing.    It seems like (at least) answers with a score of -10 or lower cause issues with formatting on mobile.  I took a look at  on Ask Ubuntu using the Android app and saw this:    It seems like there isn't enough room horizontally to display three characters with that font size, so it breaks the third one onto another line.  This issue doesn't show up in highly upvoted questions or answers, as the font size is just lowered to fit:    So it looks like the hyphen isn't counted by whatever chooses the font size, causing the line break.  I'm using Cyanogenmod 13 on a Verizon Note 4 (DPI set to 520), with the Ubuntu Regular font, in case that might be relevant.  I just tested it on an iPad, and the (now) -14 shows up fine, but screen and default font size may have something to do with that:


I would like to compare 2 objects in C#, I don't want to compare their memory address on heap, I don't want to compare them by fields, properties etc. I would like to compare them by bytes, what is exactly in the memory. I've tried that: Assert.True(Memory.Equals(x, y)); but VS says that this can be simplified and I just can use Equals and also I see that the Equals from Object class is going to be executed instead of the one from Memory. Question: How to compare memory contents?

I have two complex (i.e. objects with string, int, double, List and other home made data type) objects of the same type. I would like to compare the content of both of them to ensure that they are identical. Note: The object doesn't implement .Equals (I have no control on that) and doesn't implement IComparable.   Is there a generic way (reflection?) to compare the content of the two objects?  Thanks!


The  description is as follows:      AngularJS is an open-source JavaScript framework. Its goal is to augment browser-based applications with Model–View–Controller (MVC)   capability   But, according to the Angular website, it is now MVW:     AngularJS is what HTML would have been, had it been designed for building web-apps. Declarative templates with data-binding, MVW, MVVM,   MVC   Also,  Angular 'officially' MVW:     I hereby declare AngularJS to be MVW framework - Model-View-Whatever.   Where Whatever stands for "whatever works for you".   Conclusion  I think we should update the angular tag to make it more up-to-date.

I was browsing around the new  and when I browsed to the  I was greeted with an "edit tag wiki" link. So I edited it and created some text. Very cool.  So I have a few questions.   What is the requirement to be able to edit this tag wiki? I clearly can't do it on all tags, so I'm guessing there is some activity requirement within the tag space before you get the ability to edit the wiki. What should the content be? I browsed around a little, but I couldn't find any other examples with any content. I just included some basic text for the  one. "Questions relating to the Microsoft .NET framework" with a link to http://www.microsoft.com/net/.


I came across this question and I was able to solve this question with the help of the options provided in the question and the answer turned out to be $15$. But it intrigued me to find a general statement for the solutions for these kind of problems. How can we approach a general problem like "The largest positive integer which cannot be written in the form $Am + Bn$ where $m$ and $n$ are positive integers and $A$ and $B$ are positive integers too is?" Is there a general solution statement for this problem. I looked up on the web and stumbled upon this statement from Frobenius:  Suppose that  $gcd(a,b)=1$ . Then the largest integer  $k$  for which $am+bn=k$  has no non-negative integer solution  $(m,n)$  occurs when $k=ab−a−b$ .  The problem is when I apply this statement into my problem where $a=5$ and $b=3$ then it gives me the answer as $7$ which is less than what I got as answer. Can someone please clarify this for me and give an idea to approach these kind of problems? Thanks in advance !!! PS : Just now I noticed that my answer 15 is basically $5*3$. So can we say that for our general problem statement i.e.  "The largest positive integer which cannot be written in the form $Am + Bn$ where $m$ and $n$ are positive integers and $A$ and $B$ are positive integers too is?", the answer will be $A*B$.

This seemingly simple question has really stumped me: How do I prove that the largest integer that can't be represented with a non-negative linear combination of the integers $m, n$ is $mn - m - n$, assuming $m,n$ are coprime? I got as far as this, but now I can't figure out where to go:  $mx + ny = k$, where $k = mn - m - n + c$, for some $c > 0$ $\Rightarrow m(x + 1) + n(y + 1) = mn + c$  If I could only prove this must have a non-negative solution for $x$ and $y$, I'd be done... but I'm kind of stuck. Any ideas?


I've Created a Music Player using Visual Studio 2012 Windows Form C#. now I want the user to be able to play songs in windows explorer such as other players(Windows Media Player,Winamp,etc.) with my player. I already found the way to File association!  but I need to prevent my application from running multiple instance(as WMP&... don't) and I want to get the songs Paths too to send them to my application(already started).  For example User Select 3 Songs in a directory in windows explorer & Press Enter so my application / and execute my AddFiles Function (add the supported files to playlist and ...)  I tried mutex it solves the first part(just single instance) but can't get arguments from it!  I also tried  but No chance :( it gave error!  ** I already tried "Matt Davis" Answer and it makes my application to be single instance only and bring to front part was awesome but didn't send arguments to my running process so It couldn't solve my problem!  any Help would be in advance :)  UPDATE: I don't understand while I haven't get my problem solved why experts close the question!? :| :/  UPDATE 2 (FOUND THE SOLUTION):  ok Finally I've got the solution :)   this link helped me to get paths of selected files in explorer by clicking on a context-menu item:   real easy :) Hope this help others too!

Using C# and WPF under .NET (rather than  or console), what is the correct way to create an application that can only be run as a single instance?  I know it has something to do with some mythical thing called a mutex, rarely can I find someone that bothers to stop and explain what one of these are.  The code needs to also inform the already-running instance that the user tried to start a second one, and maybe also pass any command-line arguments if any existed.


From Page 177 of differential equations demystified (2005):  We must evaluate the integral I: (1)  $$ I = \int_{\infty}^{0} e^{- s^{2}} $$    observe that: (2)  $$I \cdot I = \int_{0}^{\infty} e^{- s^{2}}\, ds \cdot \int_{0}^{\infty} e^{- u^{2}}\, du = \int_{0}^{\infty} \int_{0}^{\pi / 2} e^{- r^{2}} r d\theta dr $$   Could somebody explain these steps in better detail.  I'm not really sure how they get from (1) to the double integral in polar coordinates in (2)

How to prove  $$\int_{0}^{\infty} \mathrm{e}^{-x^2}\, dx = \frac{\sqrt \pi}{2}$$


How can i change the css of my menu link, using javascript?  <li> <a href="here is the link"> Промоции </a> </li>   Because i cant add id on <li> or <a> ! Im using opencart, and im just trying to modify a theme

How can I change the class of an HTML element in response to an onclick or any other events using JavaScript?


In , Data remembers a joke and finds it funny. He only reveals the joke's punchline:     The clown can stay, but the Ferengi in the gorilla suit has to go.   What was the complete joke? Is it mentioned anywhere?

states:     Apparently at some point during this mission, Geordi La Forge told Data a joke, which the humorless android did not "get" until years later, when he activated his emotion chip during the events of Star Trek: Generations.    Is it known what the joke is?


I have a two lamp ballast with two blue, one red, one white, and one black. How do I connect that to a one lamp fixture????

I am replacing a ballast for a single tube. The new ballast I purchased is designed for two tubes but states that it is also compatible with a single (more powerful) tube corresponding exactly to what I need.  They apparently forgot to draw the wiring diagram for the single tube setup though. The only diagram I have is for two tubes and :               Power Switch    +--------------------------+  Line 1 (H) o----/ ----------|Black    Dual Tube     Red|-----------+  Line 2 (N) o----------------|White      Rapid       Red|--------+  |                        +-----|Yellow     Start      Blue|-----+  |  |                        |  +--|Yellow    Ballast     Blue|--+  |  |  |                        |  |  +-------------+------------+  |  |  |  |                        |  |                |               |  |  |  |                        |  |       Grounded | Reflector     |  |  |  |                        |  |      ----------+----------     |  |  |  |                        |  |    .----------------------.    |  |  |  |                        |  +----|-     Fluorescent    -|----+  |  |  |                        |  |    | )      Tube 1      ( |       |  |  |                        +-------|-       bipin        -|-------+  |  |                        |  |    '----------------------'          |  |                        |  |    .----------------------.          |  |                        |  +----|-     Fluorescent    -|----------+  |                        |       | )      Tube 2      ( |             |                        +-------|-       bipin        -|-------------+                                 '----------------------'   How do I convert this to a single tube?


I can't modify my password, but i have nothing set.  I have gDebi (no pass asking). who can help me?? Please... I have Ubuntu 12.04 hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

I'm working on a Ubuntu system, and my client has completely forgotten his administrative password. He doesn't even remember entering one; however it is there.  I've tried the suggestions on the website, and I have been unsuccessful in deleting the password so that I can download applets required for running some files. Is there a solution?


I have to render this:  But the render looks blurred  Maybe is because the size? Its too small maybe?

I just rendered an image with the 1920 x 1080 resolution, but when the image was done rendering it was 960 x 540. I don't know why it is coming out different from the dimensions specified in the render, what is the reasoning behind that? This is a Cycles Render, if that makes a difference. My rendering setup below:


I was journalling, and I typed the following:     I would love to learn how to program in Haskell and Rust.   But then I realized that "love" is too strong a word. It's only true that I would enjoy learning to program in Haskell and Rust, but it's not true that I would love doing it.  So, I replaced the word "love" with "enjoy":     I would enjoy to learn how to program in Haskell and Rust.   But then I realized that this sounds awkward to my English-as-my-first-language ears.  But, it seems like the verbs "to enjoy" and "to love" should work the same? They do work the same in the following:        I enjoy line dancing.   I love line dancing.      But they don't seem to work the same in the following:        I enjoy to line dance. [this sounds awkward]   I love to line dance.      Is there a grammatical reason that "I enjoy to line dance" sounds so awkward to me?    Edit (after I accepted that this question is an exact duplicate of a different question) :  I might note that the following does sound fine to my ears, though:     I would enjoy very much to tell my boss that he can go f*** himself! I hate him so much!

I can say:     I love to read. I hate to read.   But it must be:     I enjoy to read. I enjoy reading.   What is enjoy so different?


These are some weird graphics glitches I have on Chrome. I have Intel integrated graphics and my processor is Intel i5 8400.         Notice that the second "o" in the word "Google" has two weird green circles. And the Stack Overflow logo also looks green where it should normally be orange.

I've strange blue borders around images on google chrome see for your self


So I've tried the following:   Disabled the Windows Update Service Enabled No auto-restart with logged o users for scheduled automatic update Set Windows Update to Notify to Schedule Restart and Defer Upgrade In Power Options, disabled Wake Timers under Sleep In Task Scheduler > Microsoft > Windows > UpdateOrchestrator disabled Reboot task   Yet it never fails to wake up at 6 AM sharp, starting up the computer and running all the fans at full power... waking ME up because it's in the same room.  Is there a way to completely remove this stupid automatic update? I don't know why something so simple requires so much effort to do.

I've upgraded my PC from Windows 7 Ultimate to Windows 10 Pro; overall it seems to be working fine, with small bugs here and there. One thing that I find really annoying is that Windows seems to think it is OK to install drivers and vendor-specific control panels for me.  I've always installed drivers manually to get around having all the bloatware (i.e., Realtek's audio management panels and other vendor-specific tweaking tools).  How do I stop Windows from automatically installing bloat on my custom PC, so that I can use the drivers I've exported from packages and binaries to get around bloats?  If I uninstall everything Windows automatically installed, it seems as if a reboot persists them and installs again.  Preferably I'd like to perform a clean install and have Windows skip installing any drivers automatically. Is this possible?


So here is the problem      Solve $$4^x + 6^x = 9^x$$ for $x$.   I am trying to find its real solution.  I was trying in this way!! $$6^x\left( \frac {4^x}{6^x} + 1\right) = 9^x$$ $$\left({\frac 23}\right)^x +1=\left({\frac 32}\right)^x$$ but I'm stuck . . . Will anyone help ?

Divide The whole equation by $4^x$ $$1+\left (\frac 32\right)^x=\left(\frac 32\right)^{2x}$$ Solving the quadratic equation gives $$\left (\frac 32\right)^x=\frac{1+\sqrt 5}{2}$$  NOTE: the other value was not considered since exponential is always positive  This gives us the value of $x$ as  $$x=\frac{\ln(1+\sqrt 5)-\ln 2}{\ln 3-\ln 2}$$  But the answer given is $\frac{\ln(\sqrt 5-1)-\ln 2}{\ln 2-\ln 3}$  What is going wrong?


I'm really lost about how to fill my form, as I have an invitation from my GF from Sweden, but the closest place to her is Copenhagen, not Stockholm.    Should I fill Denmark as my first entry, and leave from Denmark also, and provide my train booking to her with my application?

Lots of people would like to visit the EEA area to take holiday or to visit family or even to go for longer term visa arrangements in the Schengen zone.  In order to do this, they need a Schengen (or national) visa.  This appears to be a fairly straightforward process, but hints and tips can always be helpful.  Without focusing on any individual's circumstances, what are some helpful hints that can improve the likelihood of a successful application?


Please if someone could tell me how to show that $1\over x$ is not uniformly continuous on $(0,1)$.  I hope I've been clear enough, thanks.

I have to prove that $\frac1x $ with $x \in (0,\infty)$ is not uniformly continuous. I understand that the further you approach the $0$ the greater your $e$ and the smaller your $\delta$ becomes (in the limit even $\delta = 0 $ ?).  But I need help with the "technical" proof, can someone give me an instruction to do this?


I designed our company logo by incorporating the two first letters of our name (W and M) and then put a circle around it.  We chose a teal color that was pulled directly from the color of a lake we visited. It was by chance that the W and M happened to be reminiscent of mountains.    It's been brought to our attention that Marmot's logo may be too similar and that we should consider changing ours before it turns into a lawsuit at some point.  It doesn't look similar to me, but then again I am very attached to our logo and have no clue where we would go from here.  I'm looking for objective opinions.   Our company manufactures yoga apparel (specifically leggings) with crossover appeal amongst many sports (outdoors included).  Marmot manufactures mainly technical outdoor gear like outerwear and sleeping bags so not exactly the same market but similar.    TIA!  Our logo by itself:   Marmot's logo:

Note: This is a canonical post created so that we can close the many similar questions as duplicates as discussed in .   We have created a logo for a client and they love it. We've already started preparing the materials that will feature the new logo.   However, after we had created the logo, we found a logo for another company that looks eerily similar. We did not intentionally create the new logo to look like the one of the other company, in fact we didn't even know it existed beforehand, but it does regardless.  What should we do? Is this plagiarism? Can our client use the logo we have created? Should they? Or do we need to come up with another logo that's more different?


$\displaystyle   0\cdot \binom{n}{0} + 1\cdot \binom{n}{1} + 2\binom{n}{2}+\cdots+(n-1)\cdot \binom{n}{n-1}+n\cdot \binom{n}{n}$ $\displaystyle\frac{1}{1\cdot 2} + \frac{1}{2\cdot 3}+\frac{1}{3\cdot 4} +\cdots+\frac{1}{(n-1)\cdot n}$   How do you find the sum of these and prove it by induction? Can someone help me get through this?

I am trying to prove the summation formula using induction:  $$\sum_{k=1}^n \frac{1}{k(k+1)} = 1-\frac{1}{n+1}$$  So far I have...  Base case:   Let n=1 and test   $\frac{1}{k(k+1)} = 1-\frac{1}{n+1}$  $\frac{1}{1(1+1)} = 1-\frac{1}{1+1}$    $\frac{1}{2} = \frac{1}{2}$   True for n=1   Induction Hypothesis:   Assume the statement is true for the n-th case   $\sum_{k=1}^n  \frac{1}{k(k+1)} = 1-\frac{1}{n+1}$  Inductive Step:   Prove, using the Inductive Hypothesis as a premise, that   $$\sum_{k=1}^{n+1}  \frac{1}{k(k+1)} = \sum_{k=1}^{n}  \frac{1}{k(k+1)} + \frac{1}{(n+1)(n+2)} = 1-\frac1{n+1} + \frac{1}{(n+1)(n+2)} = \frac{(n+1)(n+2)}{(n+1)(n+2)}+\frac{-2-n}{(n+1)(n+2)}+\frac{1}{(n+1)(n+2)} = \frac{(n+1)(n+2)-2-n+1)}{(n+1)(n+2)} = \frac{(n+1)(n+2)-n-1}{(n+1)(n+2)} = \frac{n^2+2n+1}{(n+1)(n+2)} = \frac{(n+1)(n+1)}{(n+1)(n+2)} = \frac{n+1}{n+2}$$  To prove $$ 1-\frac{1}{n+2} = \frac{n+1}{n+2} $$ Multiply both sides by $n+2$ to get an equivalent expression. $$ (1-\frac{1}{n+2}) * (n+2) = (\frac{n+1}{n+2}) * (n+2)  $$ $$ n+1=n+2−1 $$  Does this all make sense? How can this be improved upon?


I have a rust program that panicked with the message thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: ParseFloatError { kind: Invalid }', src/functions.rs.inc:58:42 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.  I searched hard, but I cannot find any hints how to set the desired environment variable in cargo or rust. I found on my Linux machine /home/pi/.cargo/env and added RUST_BACKTRACE=1 in that file, but it does not makes a difference. How do I set RUST_BACKTRACE=1 to find the reason for suddenly occurring panics?

In tcsh, I have the following script working:  #!/bin/tcsh setenv X_ROOT /some/specified/path  setenv XDB    ${X_ROOT}/db setenv PATH   ${X_ROOT}/bin:${PATH}  xrun -d xdb1 -i $1 > $2   What is the equivalent to the tcsh setenv function in Bash?   Is there a direct analog? The environment variables are for locating the executable.


Let $R$ a commutative ring and let $f(x) \in R[x]$.   (i) Prove that if $(x-a)^2|f(x)$, then $(x-a)|f'(x)$.  (ii)Prove that if $(x-a)|f(x)$ and $(x-a)|f'(x)$, then $(x-a)^2|f(x)$.  Any help in order to prove the last statements? I have been trying to prove these straight forward but I cannot see how to attack this exercises, thanks.

I don't know how to start the question. The title is self explanatory. How to approach and make a formal proof?


If I recall correctly, most of the references out there, including Wolfram Alpha, define the inverse of a square matrix $A$ to be a square matrix $B$ of the same dimension such that $AB=I$. But is this really a sufficient condition? I mean, yes, if $A$ and $B$ are over commutative ring, the commutativity of $AB=BA$ comes for free, but what if they are not? Doesn't the above definition only define the $\textit{right}$ inverse? So one needs to define the $\textit{left}$ inverse as a square matrix $C$ such that $CA=I$?  Thanks.

If $A$ and $B$ are square matrices such that $AB = I$, where $I$ is the identity matrix, show that $BA = I$.    I do not understand anything more than the following.   Elementary row operations. Linear dependence. Row reduced forms and their relations with the original matrix.   If the entries of the matrix are not from a mathematical structure which supports commutativity, what can we say about this problem?  P.S.: Please avoid using the transpose and/or inverse of a matrix.


How can I use variable in for loop digits?  for example:  num="12" for i in {0..$num}; do         ... done

How do I iterate over a range of numbers in Bash when the range is given by a variable?  I know I can do this (called "sequence expression" in the Bash ):   for i in {1..5}; do echo $i; done   Which gives:     1    2    3    4    5   Yet, how can I replace either of the range endpoints with a variable? This doesn't work:  END=5 for i in {1..$END}; do echo $i; done   Which prints:     {1..5}


New to blender and I am having difficulty subtracting two objects from each other.   I have made a surface from a bezier curve which I extruded (using 2D under the geometry tab) and filled both ends. Now I want to cut a hole in both ends. So I made a cylinder with the correct diameter hoping that I could use boolean subtraction to remove the holes.  However when I select Add Modifier, Boolean doesn't even show up as an option.  Any thoughts on why that is/other ideas to try?

This question is related to .  Let me use an exemple to illustrate what I mean.  We've created a text object (made of curves). It can't be used in a boolean modifier as it won't appear in the list of usable objects in the modifier because it's a curve object.  But if we add a remesh modifier on the text, geometry is created from the shape.  The object could be used as boolean if we convert it to mesh. The remesh can't be applied on curve object.  My question is : Can we dynamicaly use the remesh modifier created geometry as real geometry or make the boolean modifier consider the text modified object as a real mesh?  The idea behind this is to be able to change the text (or any curve 3D shape) without having to make it a real mesh.  (don't hesitate to edit my poor english to make it understandable :) )


Let $k$ be a natural number, such that $k>1$.  Show that $1 + \frac{1}{2} + \frac{1}{3} + ... + \frac{1}{k}$ is not a natural number.  How I can prove this?

If $n>1$ is an integer, then $\sum \limits_{k=1}^n \frac1k$ is not an integer.  If you know , then you know there must be a prime $p$ between $n/2$ and $n$, so $\frac 1p$ appears in the sum, but $\frac{1}{2p}$ does not. Aside from $\frac 1p$, every other term $\frac 1k$ has $k$ divisible only by primes smaller than $p$. We can combine all those terms to get $\sum_{k=1}^n\frac 1k = \frac 1p + \frac ab$, where $b$ is not divisible by $p$. If this were an integer, then (multiplying by $b$) $\frac bp +a$ would also be an integer, which it isn't since $b$ isn't divisible by $p$.  Does anybody know an elementary proof of this which doesn't rely on Bertrand's Postulate? For a while, I was convinced I'd seen one, but now I'm starting to suspect whatever argument I saw was wrong.


More specific, we have an integral domain $D$, $a,b\in D$ such that $a^n=b^n$ and $a^m=b^m$ for two positive integers $m,n$ that are relative primes. I need to prove that $a = b$. Also, my teacher insist that this could be proved without the exponent laws, since we haven't proved them in general for rings.

Let $D$ be an integral domain and let $a^m=b^m$ and $a^n=b^n$ where $m$ and $n$ are relatively prime integers, $a,b \in D$.   How do I show $a=b$?


Trying to count number of files in current directory, I found ls -1 | wc -l, which means: send the list of files (where every filename is printed in a new line) to the input of wc, where -l will count the number of lines on input. This makes sense.  I decided to try simply ls | wc -l and was very surprised about it also gives me a correct number of files. I wonder why this happens, because ls command with no options prints the filenames on a single line.

I think I may be overlooking a relatively fundamental point regarding shell. Output from the ls command by default separates output with newlines, but the shell displays the output on a single line.  Can anyone explain this to me? I had always presumed that the output was simply separated by spaces, but now that I see the output separated by newlines, I would expect the output to be displaying on separate lines.  Example:  cpoweradm@debian:~/lpi103-4$ ls text* text1  text2  text3   od shows that the output is separated by newlines:  cpoweradm@debian:~/lpi103-4$ ls text* | od -c 0000000   t   e   x   t   1  \n   t   e   x   t   2  \n   t   e   x   t 0000020   3  \n 0000022   If newlines are present, then why doesn't the output display as:  text1  text2 text3


Assuming $x \in (0, \frac{\pi}{4})$ Write down a proof that $F(x) > 0 $ for all $x$'s where $F(x) = \tan(\sin x)-\sin(\tan x)$.  All I came up with was using Jensen inequity for 1st derivative using $F(x) = \log(\cos x)$ and $\alpha_1 =\alpha_2 = \alpha_3 =  \frac{1}{3}$ and gaining $3\log(\cos(2\sin x\cdot \tan x)) \geq 2\log(\cos(\sin x)) + \log(\cos(\tan x))$ but what I need to gain is this inequality: $3\log(\cos x) \geq \leq 2\log(\cos(\sin x)) + \log(\cos(\tan x))$ Any hint would be helpful:p

How prove  this inequality $$\tan{(\sin{x})}>\sin{(\tan{x})},0<x<\dfrac{\pi}{2}$$  this  PDF give  a ugly methods :   I post this solution:let     $$f(x)=\tan{(\sin{x})}-\sin{(\tan{x})}$$   then we have   $$f'(x)=sec^2{(\sin{x})}\cos{x}-\cos{(\tan{x})}\sec^2{x}=\dfrac{\cos^3{x}- \cos{(\tan{x})}\cos^2{(\sin{x})}}{\cos^2{(\sin{x})}\cos^2{x}}$$   case 1:$0<x<\arctan{\dfrac{\pi}{2}}$, then we have    $$0<\tan{x}<\dfrac{\pi}{2},0<\sin{x}<\dfrac{\pi}{2}$$   so Use AM-GM inequality we have   $$\sqrt[3]{\cos{(\tan{x})}\cos^2{(\sin{x})}}\le\dfrac{1}{3}[\cos{(\tan{x})}+2\cos{(\sin{x})}]\le\cos{\dfrac{\tan{x}+2\sin{x}}{3}}$$   use   $$\tan{x}+2\sin{x}>3x$$   so   $$f'(x)>0\Longrightarrow f(x)>0$$   case2: $\arctan{\dfrac{\pi}{2}}\le x\le\dfrac{\pi}{2}$, so   $$\sin{(\arctan{\dfrac{\pi}{2}})}<\sin{x}<1$$   since   $$\sin{(\arctan{\dfrac{\pi}{2}})}=\dfrac{\pi}{\sqrt{4+\pi^2}}>\dfrac{\pi}{4}$$   $$\Longrightarrow \dfrac{\pi}{4}<\sin{x}<1$$,so   $$1<\tan{(\sin{x})}<\tan{1},$$,so   $$f(x)>0$$   I think this inequality have other  simple methods.Thank you  It is said can use integral inequality,But I can't   In fact,we have $$\tan{(\sin{x})}-\sin{(\tan{x})}=\dfrac{1}{30}x^7+o(x^7),x\to 0$$ can see:


In Object-oriented Javascript, we can define a method inside an object as  this.myMethod = function() {  }   OR   we can use the prototype way  MyClass.prototype.myMethod = function() {  }   What are the differences between the 2 techniques ?

What's the difference between  var A = function () {     this.x = function () {         //do something     }; };   and  var A = function () { }; A.prototype.x = function () {     //do something };


I know the grammatical correct way is he doesn't but I have seen many people saying don't with singular subjects, is there any case where it's correct.  I am just learning, please ignore my mistakes if I did any here. You can tell me my mistakes any time.

Which one is correct in a sentence?        He don't    He doesn't      I guess "he doesn't" should be correct because he is third person singular but I've seen some people using do with he. Which one is correct?


I've already looked at this question:    But there is no real answer except for 10.7.  I'm trying to migrate crontab from an old drive that I can't boot so using crontab -e is out of the question.  Just need to read the user crontab file to pull existing jobs to a new server.

I want to edit my crontab file to schedule a script. Where do I find it?


I have just bought a brand new Dell computer and have been trying to get it set up to my needs. But I seem to have run in to a bit of a problem.  I am going to use this computer for mostly programming. However, I am also going to need it for schoolwork as well. To meet both requirements, I have decided to do a dual boot with both windows and Ubuntu. But when I went to set up my disk partitions, the disk manager only let me cut my windows partition in half.  A quick google search told me that this was because windows put some really important files that are required to boot windows in the middle of their disk space. Not the way I would have done it.  Anyway, a simple solution would be to just do what windows wants and simply cut the drive in half. With a 1 terabyte hard drive, I'm sure I would have plenty for Ubuntu.  But it seems wasteful doesn't it, setting aside more than half of your hard drive to an operating system you will use a lot less than half the time. Plus, I'm sure there are other people who would benefit from knowing the answer to this question.  All that I've found so far as to solutions that don't involve sketchy third-party software, is I could make a recovery disk of windows, install Ubuntu over windows, set up my partitions, reinstall windows with the recovery disk, and finally update grub. This solution could, in theory, work. Or go terribly wrong and ruin my brand new computer.  If anyone can think of any other, better ways to accomplish this goal, your advice would be hugely appreciated.

I'm absolutely new to Linux. I would like to know how to install Ubuntu alongside the pre-installed Windows 8+ OS.  Should I do it with Wubi, or through the Live USB/DVD?  What steps do I need to take to correctly install Ubuntu?


I am learning Nodejs from scratch and I would like to make it a habit of using either single quote or double quote in Node.js. I read few answers elsewhere in Stackoverflow which said that it's purely dependent on the coding style used by the team.   So, which one should I use? Or rather, which one does the expert programmers use? in Apis and elsewhere.

console.log("double"); vs. console.log('single'); I see more and more JavaScript libraries out there using single quotes when handling strings. What are the reasons to use one over the other? I thought they're pretty much interchangeable.


I created one simple regression model for predicting the amount of loan that needs to be given to a particular individual. I plotted the residual plots to understand the underlying assumptions in the regression. However, I'm not too sure how should I interpret the graph. Could someone please help.  The graph was created using the below code.   sns.residplot(y_train_preds,y_train_preds- y_train)   Attaching screenshot.

I am unable to interpret this graph. My dependent variable is total number of movie tickets that will be sold for a show. The independent variables are the number of days left before the show, seasonality dummy variables (day of week, month of year, holiday), price, tickets sold till date, movie rating, movie type (thriller, comedy, etc., as dummies). Also, please note that movie hall's capacity is fixed. That is, it can host maximum of x number of people only. I am creating a linear regression solution and it's not fitting my test data. So I thought of starting with regression diagnostics. The data are from a single movie hall for which I want to predict demand.  The is a multivariate dataset. For every date, there are 90 duplicate rows, representing days before the show. So, for 1 Jan 2016 there are 90 records. There is a 'lead_time' variable which gives me number of days before the show. So for 1 Jan 2016, if lead_time has value 5, it means it will have tickets sold until 5 days before the show date. In the dependent variable, total tickets sold, I will have the same value 90 times.  Also, as a side remark, is there any book that explains how to interpret residual plot and improve model afterwards?


I am trying to solve an exercise given in Vakil's Algebraic Geometry notes. Suppose $M$ is a finitely presented $A$-module. The $M$ fits inside an exact sequence $A^q\rightarrow A^p\rightarrow M\rightarrow 0$. I'd like to understand why in this case we get an isomorphism $S^{-1}\text{Hom}_A(M,N)\cong \text{Hom}_{S^{-1}A}(S^{-1}M,S^{-1}M)$. This problem is towards the beginning of the book, so in particular there should be a way to solve it without heavy duty commutative algebra. So far, I've only come up with the following: We can use the universal property of localization of modules so that for any map from $\text{Hom}_A(M,N)$ to $\text{Hom}_{S^{-1}A} (S^{-1}M,S^{-1}M)$ (in which the elements of $S$ are invertible), there exists a unique map from  $S^{-1}\text{Hom}_A(M,N)$ to $\text{Hom}_{S^{-1}A}(S^{-1}M,S^{-1}M)$. However, what should this map explicitly be? Is this the way to go about showing these two are isomorphic? EDIT: There is a question about the same problem, but I am specifically asking about how to construct a map between the two sets. The solution in the related question uses facts about flat modules which I am trying to eschew.

Question. Let $R$ be a ring, $\mathfrak{p}$ a prime, $M$ a finitely-generated $R$-module, and $N$ any $R$-module. Is the natural map $$\textrm{Hom}_R(M, N)_\mathfrak{p} \to \textrm{Hom}_{R_\mathfrak{p}}(M_\mathfrak{p}, N_\mathfrak{p})$$ an isomorphism (of $R_\mathfrak{p}$-modules)?  I can prove this in the case when $M$ is finitely presented: indeed, let $S$ be any flat $R$-algebra, and let $$R^m \to R^n \to M \to 0$$ be a right-exact sequence; tensoring with $S$ gives another right-exact sequence $$S^m \to S^n \to M \mathbin{\otimes_R} S \to 0$$ and applying hom functors, we get left-exact sequences $$0 \to \textrm{Hom}_R(M, N) \to N^n \to N^m$$ $$0 \to \textrm{Hom}_S(M \mathbin{\otimes_R} S, N \mathbin{\otimes_R} S) \to (N \mathbin{\otimes_R} S)^n \to (N \mathbin{\otimes_R} S)^m$$ and $S$ is flat, so tensoring the first sequence yields $$0 \to \textrm{Hom}_R(M, N) \mathbin{\otimes_R} S \to (N \mathbin{\otimes_R} S)^n \to (N \mathbin{\otimes_R} S)^m$$ but extending the sequences by $0$ to the left, and putting in vertical maps between the last two, we conclude that $\textrm{Hom}_R(M, N) \mathbin{\otimes_R} S \cong \textrm{Hom}_S(M \mathbin{\otimes_R} S, N \mathbin{\otimes_R} S)$ by the five lemma (modulo checking commutativity of diagrams). This is essentially the proof Eisenbud gives [Commutative Algebra, Prop. 2.10].  The trouble with extending it to a proof for finitely-generated modules is that we have to replace $R^m$ with a potentially arbitrary submodule $K$ of $R^n$, and that may not be free or even finitely-generated without some additional assumptions on $R$. I can't see an abstract nonsense proof of the claim, but I admit I haven't tried a bare-hands proof. However, is the claim even true?


All of the trouble I have in learning linear algebra seems to come from my lack of understanding of its applications.  I understand how to do the multiplication, and I understand that it is a necessary tool of matrix algebra, but I want to know what the multiplication actually does, or what does its result actually represent?    Any modern real world examples that are relatively simple and specific would help me immensely.  Thanks.

Multiplication of matrices — taking the dot product of the $i$th row of the first matrix and the $j$th column of the second to yield the $ij$th entry of the product — is not a very intuitive operation: if you were to ask someone how to mutliply two matrices, he probably would not think of that method. Of course, it turns out to be very useful: matrix multiplication is precisely the operation that represents composition of transformations. But it's not intuitive. So my question is where it came from. Who thought of multiplying matrices in that way, and why? (Was it perhaps multiplication of a matrix and a vector first? If so, who thought of multiplying them in that way, and why?) My question is intact no matter whether matrix multiplication was done this way only after it was used as representation of composition of transformations, or whether, on the contrary, matrix multiplication came first. (Again, I'm not asking about the utility of multiplying matrices as we do: this is clear to me. I'm asking a question about history.)


In the book Lie algebra, Humphreys, during classification of Dynkin diagrams, arrives at the equation over positive integers: $$\frac{1}{p} + \frac{1}{q} +\frac{1}{r}>1$$ and makes a comment in bracket      (This inequality, by the way, has a long mathematical history)   I suddenly stopped at that classification, and wondered How long back the history goes for this inequality?

In Humphreys' book  Introduction to Lie algebras and Representation Theory(3rd printing, p.62), the Diophantine inequality $$\frac{1}{p} + \frac{1}{q} + \frac{1}{r} > 1$$ appeared while classifying all Coxeter graphs of irreducible root systems. Under the assumption $p \geq q \geq r \geq 2 $, the possible triples turn out to be $(p,2,2), (3,3,2),(4,3,2),(5,3,2)$, which correspond to the Coxeter graph $\text{D}_{p+2}, \text{E}_6, \text{E}_7, \text{E}_8$, respectively.  It seems quite straightforward to solve the inequality in positive integers, but Humphreys said that      This inequality, by the way, has a long mathematical history.   without further comment. So I want to know if this Diophantine inequality has any important significance, or if it has appeared in other context (maybe relevant history) before.


Just a quick question about sql injections. I know that in order to do one you must enter some mysql code and enter it into a form textbox or somewhere and it would give you back the data. With my website, to protect the data i made it impossible to send the form to the database if the user uses an any '@', ';', or '/' symbols in the textbox, because those are some common symbols used to retrieve the info through injection. Do you think that i'm protected?

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?


How do I disable the the charms bar? I am surprised there is no easy way to disable the feature.  Here's what I've done so far:  1.) Disabled right edged swipe gesture in my touchpad settings. Part of the problem is solved as this was probably the most common way the charms bar would pop up. But there are still many other ways it can pop up.  2.) Used regedit and added the key "EdgeUI" with "DisableCharmsHint" set to 1 in HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\ImmersiveShell\  This stopped it from popping up whenever I moved the cursor to the top right or bottom right of the screen. I mean who ever needs to move his/her mouse there? (sarcasm)  But there's ANOTHER WAY it pops up: when I move the cursor to the top right of the screen followed by moving it downwards OR when I move the cursor to the bottom right of the screen followed by moving it upwards! How do I disable this method of invoking the charm bar?

Can someone please tell me how to disable the annoying effect that pops up when you drag cursor to top- or bottom-right corners?


Assuming that you have a lot of classes that extends the class Base.  class Base{}  class A extends Base[}  class B extends Base{}  class C extends Base{}   What must I write so that when I write a get method, I will get the class that I want?  public Base get(Class <? extends Base> clazz, final String key){     //not important. }   I want the method to return Objects of class A, B, or C, depending on the input clazz.

Consider this example (typical in OOP books):    I have an Animal class, where each Animal can have many friends. And subclasses like Dog, Duck, Mouse etc which add specific behavior like bark(), quack() etc.  Here's the Animal class:  public class Animal {     private Map<String,Animal> friends = new HashMap<>();      public void addFriend(String name, Animal animal){         friends.put(name,animal);     }      public Animal callFriend(String name){         return friends.get(name);     } }   And here's some code snippet with lots of typecasting:  Mouse jerry = new Mouse(); jerry.addFriend("spike", new Dog()); jerry.addFriend("quacker", new Duck());  ((Dog) jerry.callFriend("spike")).bark(); ((Duck) jerry.callFriend("quacker")).quack();   Is there any way I can use generics for the return type to get rid of the typecasting, so that I can say      jerry.callFriend("spike").bark(); jerry.callFriend("quacker").quack();   Here's some initial code with return type conveyed to the method as a parameter that's never used.   public<T extends Animal> T callFriend(String name, T unusedTypeObj){     return (T)friends.get(name);         }   Is there a way to figure out the return type at runtime without the extra parameter using instanceof? Or at least by passing a class of the type instead of a dummy instance. I understand generics are for compile time type-checking, but is there a workaround for this?


I've got a div, I need the bottom div to fill the remainder of the screen and show a scroll bar. The bottom div is not showing a scroll bar.      .page {   position: fixed;   top: 0;   width: 100%;   height: 100%;   margin: 0;   padding: $menu-height 0 0 0;   box-sizing: border-box; }  .sidebar {   width: 500px;   float: left;   height: 100%;   box-sizing: border-box;   background: #ddd;   border-right: 1px solid red; }  .top {   height: 200px;   background: #eee; }  .bottom {   background: #ccc;   overflow-y: auto; }  .filler-content {   height: 2000px; }

       top

         bottom

I am working on a web application where I want the content to fill the height of the entire screen.  The page has a header, which contains a logo, and account information. This could be an arbitrary height. I want the content div to fill the rest of the page to the bottom.  I have a header div and a content div. At the moment I am using a table for the layout like so:  CSS and HTML    #page {     height: 100%; width: 100% }  #tdcontent {     height: 100%; }  #content {     overflow: auto; /* or overflow: hidden; */ }

...

...

     The entire height of the page is filled, and no scrolling is required.  For anything inside the content div, setting top: 0; will put it right underneath the header. Sometimes the content will be a real table, with its height set to 100%. Putting header inside content will not allow this to work.  Is there a way to achieve the same effect without using the table?  Update:  Elements inside the content div will have heights set to percentages as well. So something at 100% inside the div will fill it to the bottom. As will two elements at 50%.  Update 2:  For instance, if the header takes up 20% of the screen's height, a table specified at 50% inside #content would take up 40% of the screen space. So far, wrapping the entire thing in a table is the only thing that works.


I'm trying to install Ubuntu 12.10 on my Sony Vaio laptop, which already has Windows 7 on it, so I can dual boot. But, when I tried, I got      This computer currently has no detected operating system   I'm installing Ubuntu from my USB drive. Is this normal?

Whenever I startup from the LinuxLive USB, and try to install Ubuntu 12.04, it only gives me two options instead of the usual 3 or 4. My options are "Replace Windows 7 with Ubuntu" and "Something Else". Whenever I go into "Something else", it looks extremely confusing. How do I install it side-by-side while using the "Something else" section? These are my partitions.   /dev/sda /dev/sda1 ntfs (104Mb, System Required Partition) /dev/sda2 ntfs (1000097Mb, Windows 7 Partition)   Or should I try reinstalling my installer on a CD rather than USB and maybe then it will have the "Install alongside" function?


I searched a lot but couldn't find any direct answer. There must be a way to figure out from which App a certain folder or file within /storage/emulated/0/ was created.

I have a rooted device, with superuser rights granted to a few apps I trust. I have often found my /system or /vendor partition mounted read/write, and some files chmoded to 0777. Similarly directories/files with random names are created/deleted (e.g. /sdcard/.a03Degpoif), .nomedia files are created inside them to hide their contents from gallery etc.  logcat/dmesg contains no traces of all this happening in background. This doesn't happen periodically but in a slapdash way, internet connectivity isn't a condition either. I have tried disabling/uninstalling apps, looking for any suspicious processes running, but couldn't identify the culprit(s).  Is there a way to figure out who is doing this?


I am using \tcbsubtitle to place a title at the top of a tcblower and want a different background color on the two portions. This results in an unwated space above the subtitle:  How do I eliminate this undesired space? References:     Code: \documentclass{article}  \usepackage[many]{tcolorbox}  \newcommand{\LoremIpsum}{% Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.% }  \tcbset{My Box Style/.style={     colback=green!20,     bicolor,       colbacklower=yellow!60,     %segmentation at break=false,% No effect     %middle=0pt,% <-- This isn't it! }}  \newtcolorbox{example}{My Box Style}  \begin{document} \begin{example}     \LoremIpsum     \tcblower     \tcbsubtitle{Subtitle}     \LoremIpsum \end{example} \end{document}

How can I correct the transition between the background-colors? The MWE:  \documentclass[a4paper]{article} \usepackage[scale=.85]{geometry} \usepackage{tcolorbox,enumitem} \tcbuselibrary{skins,xparse}  \begin{document} \noindent  \begin{tcolorbox}[skin=bicolor,title=Main Title,     colframe=red!75!black,colback=blue!10!white,colbacklower=green!10,width=0.5\linewidth,height=0.5\linewidth]     The upper part. \par ~~~\par ~~~\par ~~~\par ~~~\par ~~~\par ~~~\par ~~~\par ~~~\par ~~~ \tcblower \tcbsubtitle[before skip=\baselineskip]%       {My subtitle}     The lower part.   \end{tcolorbox}   \end{document}   and the result is:    Thanks a lot; Harald


What are the situations where Kirchoff laws cease to be valid? How we can create circuits based on lumped element discipline, and that can work in real life? We take ideal conditions, but they just are not like that in real life.

Kirchhoff's Current Law states that the net current through a node is always 0. AFAIK this derives from conservation of charge principle. My question is, is KCL applicable to any electrical component? For example is it applicable to transistors, integrated circuits, etc.  My thought is that it should be applicable, because otherwise, the component would be accumulating charge over time, which I presume is not a stable or desirable (in general) condition. Another possibility would be that the component would be "leaking charge". For example, the component would be "throwing charge into air" etc. In this case, the component is not accumulating charge but charge is being moved out of the circuit. I guess this doesn't happen in general as well.  So my question is, is Kirchhoff's Current Law is applicable to any circuit element? For example, if I add up the currents through pins of an integrated circuit at a given time by taking current directions into account, will I get 0 amperes? Similarly for any other circuit elements. Are there any cases where the net current is not 0 amperes?


how is possible in Java validate email address by RFC 822?  Are there any available official regular expression for full support RFC822?  Thank you for your help.

What are the good email address validation libraries for Java?  Are there any alternatives to ?


One of my friend told me that photon is massless but I think that (please correct me if i was wrong),  Albert Einstein's equation  $E=mc^2$.  This equation stands for energy,  now as we know energy is also, $E= hc/\lambda$ here h is planck constant and c is speed of light and $\lambda$ is wavelenght of upcoming photons wavelenght so from both equation $mc^2 =hc/\lambda$ solving further $m=h/c\lambda$ hence the photon is not massless.  Tell me where I am wrong.

Why can't photons have a mass? Could you explain this to me in a short and mathematical way?


I would like to know if when we take a second partial derivative of a function do we always get:  $$\frac{\partial^2{u}}{\partial{x} \, \partial{y}} = \frac{\partial{^2u}}{\partial{y} \, \partial x}$$  if not, what does it mean about the function if the condition happens or not?

Is the following statement $$\frac{\partial^2 f}{\partial x \, \partial y}=\frac{\partial^2 f}{\partial y \, \partial x}$$ always true? If not what are the conditions for this to be true?


Does the verb see accept an embedded clause with a bare infinitive verb like help or make(in the active voice)?

"Heard me [infinitive]" vs. "heard me [present participle]"             At that time, you wouldn't have heard me talk about it.   At that time, you wouldn't have heard me talking about it.         At that time, you wouldn't have heard me condemn it.   At that time, you wouldn't have heard me condemning it.         Which one of the above sentences are incorrect and why?


How can we show $$ \bigcup_{n\in\mathbb N}A_n = \bigcup_{n\in\mathbb N}\bigl(A_n\setminus\bigcup_{k=1}^{n-1} A_k\bigr)$$ for any family of sets?  So let $x\in \bigcup_{n\in\mathbb N}\bigl(A_n\setminus\bigcup_{k=1}^{n-1} A_k\bigr)=\bigcup_{n\in\mathbb N}\bigl(A_n\cap\bigcap_{k=1}^{n-1} A_k^c\bigr)$. So $\exists n: x\in A_n\cap\bigcap_{k=1}^{n-1} A_k^c $ and therefore $x\in A_n \wedge x\in A_1^c\wedge\dots\wedge x\in A_{n-1}^c   $. So we get $x\in \bigcup_{n\in\mathbb N}A_n.$   What happens if $A_i$ isn't pairwise disjoint? And how do you get the other way?

I'm having trouble to prove the following question:  Supose $\{A_n\}_{n\in\mathbb{N}}$ is a family of sets such that $A_1\subset A_2\subset A_3\subset\ldots$ (it's possible to have $A_n=A_{n+1}$). I need to prove that $$\lim_{n\to\infty}A_n = A_1\cup\bigcup_{n=2}^\infty(A_{n}\backslash A_{n-1}).$$  I'm not sure if this is useful, but I proved that $A_{n}\backslash A_{n-1}$ and $A_{n'}\backslash A_{n'-1}$ are disjoint if $n\neq n'$.  Thank you.


I have several Microsoft Store programs installed.  For example, MineSweeper is installed via Microsoft Store. Looking my Start Menu, I can see those installed programs, including MineSweeper which is in the M section of the Start Menu. However, using Explorer, I cannot find the MineSweeper.lnk shortcut file. I searched well known paths:  %ProgramData%/Microsoft/Windows/Start Menu/Programs (C:\ProgramData\Microsoft\Windows\Start Menu\Programs) (also accessible via [Environment]::GetFolderPath('CommonStartMenu') %APPDATA%/Microsoft/Windows/Start Menu/Programs (C:\Users\user1\AppData\Roaming\Microsoft\Windows\Start Menu\Programs) (also accessible via [Environment]::GetFolderPath('StartMenu')  and less well known Start Menu paths:  %APPDATA%/Local/Packages/Microsoft.549981C3F5F10_8wekyb3d8bbwe/LocalCache/Roaming/Microsoft/Windows/Start Menu %APPDATA%/Local/Packages/Microsoft.DesktopAppInstaller_8wekyb3d8bbwe/LocalCache/Roaming/Microsoft/Windows/Start Menu  Explorer has View → Hidden items checked. Since MineSweeper is installed via Microsoft Store, a right-click on the Start Menu entry MineSweeper does not display the Open file location option. What is the path where Microsoft Store saves the .lnk shortcut files that appear as Start Menu entries?  Using Windows 10 Pro.

I am trying to fix start menu damage after windows 10 install.  Currently, I removed all files from known locations of start menu files, but still have some entries in Start Menu.  Here is the proof folders are empty:    And here is the proof that I still have some entries in Main Menu:    What are all locations of Start Menu folders in Windows 10?


In my exercise I'm supposed to validate phone numbers, which of the correct are :  1234567890 123-456-7890 123.456.7890 (123)456-7890 (123) 456-7890 456-7890   I've tried [(]?[0-9][0-9][0-9][).-]? ?[0-9][0-9][0-9][.-]?[0-9][0-9][0-9][0-9], but it seems  it also accepts something like (123.456-7890. How I can handle this? Or I should take completely different way ?  Here are some invalid phone numbers:  123-45-6789 123:4567890 123/456-7890

I'm trying to put together a comprehensive regex to validate phone numbers. Ideally it would handle international formats, but it must handle US formats, including the following:   1-234-567-8901 1-234-567-8901 x1234 1-234-567-8901 ext1234 1 (234) 567-8901 1.234.567.8901 1/234/567/8901 12345678901   I'll answer with my current attempt, but I'm hoping somebody has something better and/or more elegant.


So lets prove the general statement $$ \begin{align} (-a)(-b)=ab \\ \because ab + (-ab)=0 \\ \therefore (-a)(-b)+(-ab)=0 \ \land \ (-a)(-b)+(-(-a)(-b))=0 \\ \therefore -1 \cdot (-a)(-b)=-ab \\ by \ the \ definition \ of \ associative \ law \\ (-1 \cdot -a) \cdot (-b)= -ab \end{align} $$ and now i want to prove $(-1 \cdot -a) = a$ which brings me back to the question .

Someone recently asked me why a negative $\times$ a negative is positive, and why a negative $\times$ a positive is negative, etc.  I went ahead and gave them a proof by contradiction like so:  Assume $(-x) \cdot (-y) = -xy$  Then divide both sides by $(-x)$ and you get $(-y) = y$  Since we have a contradiction, then our first assumption must be incorrect.  I'm guessing I did something wrong here. Since the conclusion of $(-x) \cdot (-y) = (xy)$ is hard to derive from what I wrote.  Is there a better way to explain this?  Is my proof incorrect?  Also, what would be an intuitive way to explain the negation concept, if there is one?


I'm curious to what makes something qualify as a ground? I do some electrical work on my car. And the way I understand it, is that the chassis of the car is used as ground because it's such a big metal piece that the chassis doesn't build up enough charges to be considered charged. Therefore it's a 'zero potential'.   But how big does the metal object have to be, compared to the (e.g.) battery it's connected to. In other words, what makes the metal object qualify as a ground?  The reason for asking this question is because in many instructions I am told to "connect the other wire to a ground", and I keep asking myself: Well, what is a ground, and what is not?

I'm a bit confused about the concept of ground, and perhaps voltage as well, particularly when trying to analyze a circuit. When I learned about Ohm's law in grade school, I learned how to apply the law to calculate current, voltage, and resistance of simple circuits.   For instance, if we were given the following circuit:    We would be could be asked to calculate the current passing through the circuit. At the time, I'd simply compute (based on the rules given) 1.5V/1Ohms=1.5A.  Later on, however, I learned that the reason the voltage of the resistor would be 1.5V is because voltage is really the difference in potential between two points, and that the difference of the voltage across the battery would be the same as that of the resistor (correct me if I'm mistaken), or 1.5V. I got confused, however, after the introduction of the concept of ground.   The first time I tried to do the current calculation for a circuit similar to the previous circuit on a simulator, the program complained about not having a ground and "floating voltage sources". After a bit of searching, I learned that circuits need ground as a reference point or for safety reasons. It was mentioned in one explanation that one can pick any node for ground, although it's customary to design circuits so there is a "easy place" to pick ground.   Thus for this circuit    I picked ground at the bottom, but would it be okay to pick ground between the 7 ohm and 2 ohm resistor - or any other place? And what would be the difference when analyzing the circuit?  I've read that there are 3 typical ground symbols with different meanings - chassis ground, earth ground, and signal ground. A lot of circuits I've seen used in exercises either use earth ground or signal ground. What purpose is there in using earth ground? What is the signal ground connected to?  Another question: since the ground is at unknown potential, wouldn't there be current flowing to or from ground to the circuit? From what I've read we treat the ground as 0V, but wouldn't there be some sort of effect because of a difference in potential of the circuit and ground? Would the effect be different depending on what ground was used?  Finally: In nodal analysis, one customarily picks a ground at the negative terminal of the battery. However, when there are multiple voltage sources, some of them are "floating". What meaning does the voltage of a floating voltage source have?


Code:  $gameID= $_GET['gid']; $con = mysql_connect($dbserver,$dbuser,$dbpassword); if (!$con) {    die('Could not connect: ' . mysql_error()); }  mysql_select_db($dbname, $con);  $sqlselect="SELECT * FROM games WHERE gameid=" . $gameID; $result = mysql_query($sqlselect);  $row = mysql_fetch_array($result); $gwidth =  $row['width']; $gheight = $row['height'];  if($gwidth > 700)<br /> {   $gwidth = $gwidth * 0.75;   $gheight = $gheight * 0.75; }   can anybody tell me how to secure this sql queries ?  VULNERABILITY: CLASSIC MYSQL INJECTION

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 inherited VM server with two guests (with Debian) running with static IPs (they work fine).    I created new guest (Debian 8.5) and configured it with static IP through /etc/network/interfaces in same way the other guests are configured (standard iface eth0 inet static etc).    On this guest once a 24h IP reverses to DHCP configuration but after restarting eth0 it works with static IP again.    All guests are on the same vSwitch and in the same virtual network (connected to the same Physical Adapter).    I am managing VMs with vSphere Client 5.5.  /etc/network/interfaces on the guests:  This one is working correctly:  # The loopback network interface   auto lo iface lo inet loopback  # The primary network interface allow-hotplug eth0 iface eth0 inet static     address 192.168.1.40     netmask 255.255.255.0     broadcast 192.168.1.255     gateway 192.168.1.1       dns-nameservers 8.8.8.8   This one is keep going back to dhcp:  # The loopback network interface   auto lo iface lo inet loopback  # The primary network interface allow-hotplug eth0 iface eth0 inet static     address 192.168.1.10     netmask 255.255.255.0     broadcast 192.168.1.255     gateway 192.168.1.1       dns-nameservers 8.8.8.8 4.4.4.4

I have a Linux server (Rasperry Pi using Raspbian as OS) that should be using only static IP.   However I noticed that it also has got IP from DHCP server (The IP given out by DHCP is 192.168.111.2). According to network settings the server should be only using static IP (192.168.111.100).  The contents of /etc/network/interfaces:  auto lo iface lo inet loopback  auto eth0 iface eth0 inet static address 192.168.111.100 netmask 255.255.255.0 gateway 192.168.111.1 dns-nameservers ip1 ip2   Despite using static configuration I can SSH to the device also using the IP given by DHCP. Also it appears that ntpd is using the wrong IP as well as the correct one.  Output of Netstat:  udp        0      0 192.168.111.2:123       0.0.0.0:*                           2774/ntpd udp        0      0 192.168.111.100:123     0.0.0.0:*                           2774/ntpd   According to ifconfig the IP 192.168.111.2 is not used:  eth0      Link encap:Ethernet  HWaddr b8:27:eb:be:18:1c           inet addr:192.168.111.100  Bcast:192.168.111.255  Mask:255.255.255.0           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1           RX packets:138099 errors:0 dropped:0 overruns:0 frame:0           TX packets:81146 errors:0 dropped:0 overruns:0 carrier:0           collisions:0 txqueuelen:1000           RX bytes:95954711 (91.5 MiB)  TX bytes:27076870 (25.8 MiB)   ps -ef | grep dhcp shows that I have a DHCP daemon running:  root      2000     1  0 Oct07 ?        00:00:06 /sbin/dhcpcd   How do I disable the DHCP daemon from starting and make sure that my server uses only the static?


I need to grab the wireless password from my DIR-651 router and put in my phone.  I set the router up several months ago and haven't used wireless since.  I have access to the DIR-651 admin page via wired connection, but I am not finding where the wireless passwords are located.  I've looked all over the Manual Wireless setup page.  There is a "pre shared" key at the bottom, but even that is obscured (dots).

If you have a laptop running XP that is able to connect to a wireless network fine, but you don't know the password it's using, is there any way to find it out so that a second laptop can also connect?


I've been using Ubuntu (13.10) for a couple of months, and I really liked. But it crashed often and that's something that I didn't liked. I was able to run all my files in my terminal without any problem, like my favourite games. And also the executable files. I was able to run them perfectly.   Then elementary Luna OS came out and I decided to give it a try. When I installed was really quick, but after some days I realized that I couldn't open most of my files on the terminal. Just a few, I can't play games anymore because of that problem. Also, I can't open executable files.   So, I decided to reinstall Ubuntu, and guess what? I wasn't able to do nothing! my games and everything, I couldn't open them because the terminal didn't let me. Always displaying the message "no such file or directory" while the file actually exist.   Also tried in Linux mint, same thing. I've tried everything, can't do anything. Could some of you help me.  All of my desktops were x64 bits edition. Right now I'm running Linux mint 16 petra cinnamon desktop x64.   How to solve this?

I've downloaded a game (Shank) but the bin file doesn't run. The error that is shown when I try to launch the executable is:  bash: ./shank-linux-120720110-1-bin: No such file or directory


I am looking for the title of a book telling the story: an object which at first seems to be a comet comes into orbit of Earth. It turns out to be a tube? that is a fixed size but inside it is endless. It gives access to multiple parallel Earths.     The title was one word (like "eos" => not). I read this book in the early 90s. I'm not sure if I read it in English or Dutch but I think the original language was English.

I read this book many years ago and it had a nice plot. For the life of me I can't remember the name or author so I need help.  Story: one asteroid shaped object appears close to Earth orbit or in the Sol system.  People get on board and start exploring. They find machines/computers that can teach them anything in a very short time (languages, crafts etc).  Towards the end, something happens and one of the characters goes into a long tunnel where he/she opens a portal in time with the help of a device he/she has.  In the epilogue it states that he has been transported back in time to Egypt.  I think there were no pyramids.  Sorry for being brief but this is all I remember. Any help would be appreciated. Thanks.


I have a table containing mathematics with sub and superscripts. These touch both the lines above and below in the table.  I tried quite a few alternatives but have not been able to find anything that gives suitable spacing in the rows without also messing up the spacing of the title row (ie making the headings too tightly left aligned). Any pointers on the best approach for this would be appreciated.  Here is my current result (I am using the array package):    \begin{table}[htbp] \begin{center}     \begin{tabular}{| m{2.7cm} | m{8cm}|}         \hline         \textbf{Marginalised term} & \textbf{3 variable terms} \\         \hline \hline          $H_\partial^{12}(\{12\})$ &          $\begin{aligned}              &H_\partial^{123}(\{12\}) + H_\partial^{123}(\{3\}\{12\}) \\             &+ H_\partial^{123}(\{12\}\{13\}) + H_\partial^{123}(\{12\}\{23\}) \\              &+ H_\partial^{123}(\{12\}\{13\}\{23\})               \end{aligned}$ \\         \hline         $H_\partial^{12}(\{1\})$ &           $H_\partial^{123}(\{1\})+H_\partial^{123}(\{1\}\{23\})+H_\partial^{123}(\{1\}\{3\})$ \\         \hline         $H_\partial^{12}(\{2\})$ &           $H_\partial^{123}(\{2\})+H_\partial^{123}(\{2\}\{13\})+H_\partial^{123}(\{2\}\{3\})$ \\         \hline         $H_\partial^{12}(\{1\}\{2\})$ &           $H_\partial^{123}(\{1\}\{2\})+H_\partial^{123}(\{1\}\{2\}\{3\})$ \\         \hline   \end{tabular} \end{center} \end{table}   Setting extrarowheight fixes the top spacing for the lower three rows, but they still all touch the lower hline and the first row touches both above and below.   Adding extrarowheight doesn't work:    Nor does arraystrectch (top row touches and vertical centering off):

I was working on some calculus today and tried to typeset a matrix of partial derivatives and ran into some trouble. Here is my code:  \documentclass{minimal} \usepackage{mathtools} \begin{document} \begin{equation} \begin{pmatrix}     \frac{\partial f^1}{\partial x_1}   & \frac{\partial f^1}{\partial x_2}\\     \frac{\partial f^2}{\partial x_1}   & \frac{\partial f^2}{\partial x_2} \end{pmatrix} \end{equation} \end{document}   As can be seen, the output results in the subscripts from the denominators of the top row on the matrix with the superscripts from the numerators of the bottom row on the matrix. Is there an easy way to avoid this?


I have a div with such content:
Red

Yellow

Cyan

Luke Skywalker

   I use this jQuery function to replace text inside the divs. After all I append 2 more .foobar divs to #data:  $(function() {     $(".foobar").each(function() {         $(this).html("Black");     });     appendDiv(); });  function appendDiv() {     $("#data").append("
White
");     $("#data").append("
Orange
"); }   And here I don't know how to apply inited .each function to appended divs. I've tried that, but it didn't worked for me:  $("#data").on("load", ".foobar", function(){     $(this).html("Black"); });   How to apply .each function to appended html?

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


Let $A\in M_{n}(\mathbb R)$ and $\mathrm{tr}(A^{m})=0$ for every positive integer $m$. Is $A$ nilpotent? Is $A^{2}-I$ invertible?

Let $A$ be an $n\times n$ complex nilpotent matrix. Then we know that because all eigenvalues of $A$ must be $0$, it follows that $\text{tr}(A^n)=0$ for all positive integers $n$.  What I would like to show is the converse, that is,      if $\text{tr}(A^n)=0$ for all positive integers $n$, then $A$ is nilpotent.   I tried to show that $0$ must be an eigenvalue of $A$, then try to show that all other eigenvalues must be equal to 0. However, I am stuck at the point where I need to show that $\det(A)=0$.  May I know of the approach to show that $A$ is nilpotent?


I am connecting an external drive from Intenso to my Ubuntu 16.04 LTS. Both in Nautilus and on the command line I am not allowed to write/delete/change files and folders. For instance, mkdir says: mkdir: cannot create directory ‘test’: Read-only file system  I tried the accepted answer from this question:  However, then I can e.g. create files for a few minutes. Afterwards the drive appears read-only again.  Any idea how to overcome this?

I have an NTFS partition. The idea is I can use this for data on either Ubuntu Mate or Windows 10 dual boot. It worked fine when I first installed Mate, but recently I no longer have the delete option when I right-click on a file or folder. The delete key does nothing. I also can't paste into the partition (Paste greyed out). It's as if the whole partition is read-only. In Gparted, the partition is marked with a key. Does this mean anything? I'm not aware of having changed anything, however, Windows recently did a big update - have they hijacked my drive?  I've read related posts, but people speak of returned errors - I have no errors, just nothing happens. Also, suggested solutions seem far too technical for what must surely be a simple tick-a-box fix!  Please note - for me the Terminal is where I get off a train and Sudo sounds like a Japanese noodle dish. ;) GUI's preferred if possible! Thanks for your patient help!