remove white space from the end of line in linux
How to remove trailing whitespaces with sed?
$ d = \gcd(a,b)\Rightarrow\ \gcd(a/d,b/d) = 1$ How to create a page like this? I'm a LaTeX newbie. I want to create a page layout like in the picture below on every page.  Can someone help please? Thanks. Undefined control sequence \documentclass First of all I would like to thank you because you helped me out a lot with all your answers to the already online questions.  Now, here is my problem. I am trying to do a bibliography file with TeXworks but I get this error when I try to compile (pdfLaTeX+MakeIndex+bibTeX):      This is pdfTeX, Version 3.1415926-2.4-1.40.13 (MiKTeX 2.9 64-bit)     entering extended mode     ****PATH here******     ! Undefined control sequence.     l.1 \documentclass         [a4paper,11pt]{report}   I've been reading some similar questions but I don't find the way to fix it (maybe I am missing something). I found one that says that I am trying to compile a LaTeX file using TeX compiler but I don't know how to change the configuration.  This is the .bib fiel content:      \documentclass[a4paper,11pt]{report}     \usepackage[english]{babel}     % faire de l'anglais     \usepackage[latin1]{inputenc}   % accents dans le source     \usepackage[T1]{fontenc}        % accents dans le DVI     \usepackage{url}     \begin{document}      @Article{ref11, author={Danihelka, Jiri and Kencl, Lukas}, journal={Cloud Futures Workshop 2012 }, title={Colaborative 3D Environments over Windows Azure}, year={2012}, month={May}, pages={}, note={}     }      @book{ref12, author = {Lee, Henry and Chuvyrov, Eugene},     title = {Beginning Windows Phone 7 Development},     publisher = {Apress},     volume = {},     number = {},     series = {},     address = {},     edition = {Second edition},     year = {2011},     month = {July},     note = {}     }      @Article{ref13, author={}, journal={}, title={Cloud computing}, year={}, month={}, pages={}, url={\url{http://en.wikipedia.org/wiki/Cloud_computing}}     }      \end{document} I'm always on the hunt for free stock images to use while I design, what are some good resources for images that are under a a royalty free or creative commons licence? I have white blank on the posts.    App Version: 1.0.89 Device Manufacturer: Meizu Device Model: m2   OS Version: 5.1 (1464689330)    I can't see the questions and the answers and the comments.  I saw that it's a common issue..  Does it have a fix?   EDIT -  I saw  answer. This answer is ~2 years old. It says that it will fix in the next update.  His version is 1.0.59 - mine is 1.0.89. Huge different.   The problem is still exists! Considering the irreducible (by condition) polynomial $f=X^4-2aX^2+b\in\mathbb Q[X]$ and the field extension $K=\mathbb Q(\sqrt{a^2-b})$ of $\mathbb Q$, I want to show the following result:    For $[L:\mathbb Q]=4$ we have $\sqrt b\in K$ where $L$ is the splitting field of $f$.   My thoughts so far: The four roots of $f$ are $\pm\sqrt{a\pm\sqrt{a^2-b}}$. If $L$ is of degree $4$ it must be primitive since $f$ is irreducible, so $L=\mathbb Q\left(\sqrt{a+\sqrt{a^2-b}}\right)$. Then, by multiplying the two roots $\sqrt{a+\sqrt{a^{2}-b}}\cdot\sqrt{a-\sqrt{a^{2}-b}}=\sqrt{b}$ we have that $\sqrt{b}\in L$. Now I want to look at $$\mathbb Q\subset K\subset K(\sqrt b)\subset L$$ and differentiate some cases. The case where $[L:K]=1$ is trivial and the case $[L:K]=4$ can't happen because if we square any root and subtract $a$, we get $\pm\sqrt{a^2-b}\in K$ which means $[L:K]\leq 2$. So let's look at the case where $[L:K]=2$. As I see it, we get two subcases:   For $[L:K(\sqrt b)]=2$ we have $K(\sqrt b)=K$ which finishes the proof. For $[L:K(\sqrt b)]=1$ we have $K(\sqrt b)=L$. This means that $L$ is also the splitting field of $(x^2-b)(x^2-(a^2-b))$. Is this a contradiction? How do I finish this case? "Hot" tab in is badly skewed and misleading - time to replace it with actual hot questions? Each site got a &quot;hot&quot; tab, where its contents are calculated based on . However take a look on the screenshots below and see for yourself that &quot;hot&quot; got nothing to do with many of the questions listed there. :    :    As you can see, there are questions with negative score, no answers, and even closed. I won't be surprised to see spam in there as well. This can't be any worse. What I suggest, instead of fixing the formula or patching it, simply have the hot tab show the same questions as the Hot Network Questions sidebar. (from the specific site only, of course.) Since the hot questions &quot;pool&quot; (as seen ) is limited to 100 for the whole network, either expand it or have the per-site list show questions with less hotness points - it would still be better than what we have now. If $g \circ f$ is surjective, show that $f$ does not have to be surjective? Suppose $f: A \to B$ and $g: C \to D$ are functions, and that $B ⊆ C$.  I need to come up with an example where $g \circ f$ is surjective but $f$ is not. I'm confused on how exactly to do that, but I understand that to show something is surjective you have to have the range of the function equal to the codomain of the function. Here's my attempt:  So if $g(x) = x^2$ with a codomain of $ℝ$, and $f(x) = \sqrt{x}$ with a codomain of $ℝ$, then $g(f(x)) = (\sqrt{x})^2 = x$. Since the range of this function and codomain are the same, this is surjective.  But, since $f(x) = \sqrt{x}$, its range is only $[0, ∞)$, which is smaller than its codomain of $ℝ$, meaning $f$ is not surjective. I have a site which is running under SharePoint 2013. Via REST I am trying to retrieve the file and folder directory for that site. There are several similar questions on this site related to recursively retrieving all of the files and folders for a given a folder:       The answers provided therein led me to the following URI:     /_api/web/Lists/GetByTitle('Documents')/Items?$expand=Folder&amp;$select=Title,FileLeafRef,Folder/ServerRelativeUrl   Which from what I can tell does retrieve all of the files and folders from the given starting path.  However, I am missing something. When reading through the returned XML I cannot figure out where a given file goes. Meaning that I have info on how to retrieve file bros.pdf, but cannot determine that it is in the documents/super/mario/ folder.  For the file items I've tried to retrieve the ServerRelativeUrl property, but have not succeeded though the folders seem to. Is there some identifier in the XML that I am missing? When doing a recursive RESTful query how do I determine where a given file belongs? What is the meaning of $\exp(\,\cdot\,)$? What is the meaning of the notation $\exp(\text{expression})$ ?  I think that it's something of the form $a^\text{expression}$ but does it mean that the base $a=e$ or can it be any base? Number of non-decreasing functions? Let $A = \{1,2,3,\dots,10\}$ and $B = \{1,2,3,\dots,20\}$. Find the number of non-decreasing functions from $A$ to $B$.  What  I tried: Number of non-decreasing functions = (Total functions) - (Number of decreasing functions) Total functions are $20^{10}$. And I think there are ${20 \choose 10}$ decreasing functions. Since you choose any $10$ codomain numbers and there's just one way for them to be arranged so that the resultant is a decreasing function. However my answer doesn't match. Where am I going wrong? How can I directly compute the non-decreasing functions like without subtracting from total? sum of polynoms of given property Big Endian vs. Little Endian in Qiskit I've noticed that Q# favors Little Endian. Meaning that most operations are designed for this type of encoding.  Is is it the same with Qiskit? Need for a side book for E. Soper's Classical Theory Of Fields I am reading now E. Soper, Classical Theory Of Fields, now and sometimes it is very hard to follow the equations. So I need a side book on  to read it comfortably. Landau &amp; Lifshitz's book is not helping as its content and topics are very much different. Android app "Unknown error" when uploading photo Spent a half hour on this. Android 5.1.1 latest version SE app (Play Store won't let me update so latest).   Tried to upload photo into an answer. "Something went wrong".  Did tricks to reduce photo size to 275k -- same.    45k rep on the stack.  Here is the photo..... oh wait.  How do I solve? Check for internet connection with Swift What is the iPod touch's screen sensitive to? We all know that _spPageContextInfo is a very useful thing in Client side development. I need something equivalent of _spPageContextInfo in SPFX. Currently I am unable to use it directly from typescript. It gives error like     Can not find '_spPageContextInfo'   Finally, I have gone through the API documentation of  and  found . PageContext has dependence with . My qestion is: How to use PageContext? I need to use it my BaseService class. constructor of my class is:  constructor(private $http: ng.IHttpService, private $q: ng.IQService, serviceScope: ServiceScope) {     serviceScope.whenFinished(() =&gt; {       this.pageContext = new PageContext(serviceScope);       console.log(this.pageContext);     });   }   Inside the constructor serviceScope is undefined. I know the reason: As I am not injecting/initialising serviceScope anywhere like other angular services. So what is the approach of injecting/initialising serviceScope in angular service class? How to get all possible combinations of a list’s elements? Mathematical induction for inequalities: $\frac1{n+1} + \frac1{n+2} + \cdots +\frac1{3n+1} > 1$