Is there a way to create logical or as a sum-class symbol?
How to look up a symbol or identify a letter from a math alphabet or other character?
Explain why $E(X) = \int_0^\infty (1-F_X (t)) \, dt$ for every nonnegative random variable $X$ The topic which haunted me for two years until I gave up on it. But now I am doing engineering and this topic suddenly popped out of my textbook from nowhere. I seriously need to understand this topic because I wasn't able to do so in the past. I have read many book on 'energy' and it came to nothing. Maybe just because the many books I have read all said 'energy' is something which doesn't 'exist'! It is 'abstract'! It is just a number which represents the state or orientation of a system. But then I see so many examples that 'uses' energy to do 'work'. But the question here is that if anything doesn't exist in this universe, then how can the same thing be used to do something that exist?  My problem is that I didn't understood the topic 'energy' and all the other topics related to it (work, power etc.) How to determine the genre of a song? I listen to many songs and I always wonder how the genre of a song is determined. Is it by listening to the song, or by the song's info like the artist, year released and so on? Speed of light when accelerating I'm studying special relativity and saw the 2 postulates of Einstein. The most remarkable one for me is the universal speed of light. Einstein postulated that the speed of light in vacuum is the same for all inertial observers, regardless of the motion of the source. But what if we are accelerating and we are changing from one inertial frame to another, how will we observe the speed of light? Is it still the same? I suggest it's not? Because I alread saw a small introduction to general relativity where the light will bend in a gravitational field and therefore also when you accelerate. So does the speed of light change because it bends? Vertical line for the the right margin in Notepad++ Why is super.super.method(); not allowed in Java? I covered hyperbolic trigonometric functions in a recent maths course. However I was never presented with any reasons as to why (or even if) they are useful.  Is there any good examples of their uses outside academia? Can Ubuntu use all my 4GB of RAM? Received an email intended for another person How to find "file-release" in OS X El Capitan 10.11.6? I can not find file-release through command line on OS X El Capitan Version 10.11.6. On my virtual machine in Ubuntu I can do "ls /etc/*release" and it shows me two files with all needed information:  $ cat /etc/redhat-release  Red Hat Enterprise Linux Server release 7.0 (Maipo)  $ cat /etc/os-release  NAME="Red Hat Enterprise Linux Server" VERSION="7.0 (Maipo)" ID="rhel" ID_LIKE="fedora" VERSION_ID="7.0" PRETTY_NAME="Red Hat Enterprise Linux Server 7.0 (Maipo)"   No idea how to find the file with release information on Mac. Please give me a hint or a hint how to search it? How do I draw shapes inside a tikz node? I know how to draw different shapes using tikz, like this:  \documentclass{minimal} \usepackage{tikz} \begin{document}  \begin{tikzpicture} \draw (0,0) ellipse (1 and 1.5)       (0,2.5) circle (1)       (2.5,0) circle (1.5); \end{tikzpicture}  \end{document}     However, I would like to put a number of different shapes together inside a node, and I couldn't yet find a simple way to do that. I will make a little figure to include in a large diagram which is already made of several nodes.  If this is not possible, or not easy, then how do I include a JPG or EPS file in a node?  Thank you! Why aren't search engines indexing my content? If $S$ is a nonempty subset of group $G$, then $S^{|G|}$ is a subgroup of $G$. Let $G$ be a group with $|G| = n$ and let $ \emptyset \ne S \subseteq G$.   I want to show that $S^n$ is a subgroup of $G$ where by $S^n$ I mean the set $\lbrace s_1\cdots s_n \; | \; s_i \in S\rbrace$. What is "Go" in cribbage? I've played a fair bit of cribbage, but I've never heard of scoring one point for "Go" (as mentioned in this other question: ).  What is it, and what impact does it have on the game? Is there a difference between "==" and "is"? My  has failed me.  In Python, are the following two tests for equality equivalent?  n = 5 # Test one. if n == 5:     print 'Yay!'  # Test two. if n is 5:     print 'Yay!'   Does this hold true for objects where you would be comparing instances (a list say)?  Okay, so this kind of answers my question:  L = [] L.append(1) if L == [1]:     print 'Yay!' # Holds true, but...  if L is [1]:     print 'Yay!' # Doesn't.   So == tests value where is tests to see if they are the same object? How can I find the method that called the current method? How to delete all music on my iPhone How do I delete all the music on my iPhone.  I tried doing it through iTunes but it says my collection is not managed by iTunes and I don't want to erase and sync because all my apps are nicely backed up and sorted with iTunes.  I have only seen a way of deleting song by song on the phone. Number reference headline I try to number the header of my references. I succeeded to add the number to the table of contents, but I can't get it to work for the header.  To add the number to the toc I used:  \addcontentsline{toc}{section} \protect\numberline{\thesection}References}   If I try the same for \refname, I get 5References without space.   \renewcommand{\refname}{\protect\numberline{\thesection References}}   When I put the references title outside the curly brackets, it's shown in a new line. What am I missing here? The full bibliography call looks like this:  \renewcommand{\refname}{\protect\numberline{\thesection References}} \addtocounter{section}{1} \cleardoublepage \phantomsection \addcontentsline{toc}{section}{\protect\numberline{\thesection}References} \bibliographystyle{apacite} \bibliography{bachelor}   EDIT 1:  As @TeXnician stated, a tilde would solve the problem. It is not very elegant, though, as I have to use approximatly three of them to get the same space as in the other headlines.   \renewcommand{\refname}{\protect\numberline{\thesection~~~References}}   EDIT 2: @Werner suggested a shorter solution, but it throws multiple errors, when I try to integrate it into my .tex file. Here's a short reproducable example which replicates the errors.  \documentclass[12pt]{article} \usepackage[utf8]{inputenc} \usepackage[margin=1.1in]{geometry} \usepackage{listings} \usepackage{apacite} \usepackage{natbib}  \begin{filecontents}{mybib.bib}  @Article{draxler2010sample,     author    = {Draxler, Clemens},     title     = {Sample size determination for Rasch model tests},     journal   = {Psychometrika},     year      = {2010},     volume    = {75},     number    = {4},     pages     = {708--724},     publisher = {Springer}, }  \end{filecontents}   \begin{document}  \tableofcontents      \section{First Chapter}  \citep{draxler2010sample}  \let\oldsection\section% Store \section in \oldsection \renewcommand{\section}[2]{\oldsection{#2}}% Update \section to gobble * \bibliography{mybib} \bibliographystyle{apacite}  \appendix  \section{R Code}  \subsection{Greedings Function}  \begin{lstlisting}     print("Hello World") \end{lstlisting}  \end{document} make tail -f exit on a broken pipe I want to watch a file until a bit of text appears  I found this answer:   but when I tried it on ubuntu, it doesn't exit:  $ echo one &gt; test.txt $ echo two &gt;&gt; test.txt $ echo three &gt;&gt; test.txt $ echo four &gt;&gt; test.txt $ cat test.txt | sed '/w/ q' one two $   works as expected.  however when I try to tail the file  $ tail -f test.txt | sed '/w/ q' one two   it never exits.  tail does not stop even though the pipe is broken.  Does anybody know how to make tail exit when sed exits? MySQL strip non-numeric characters to compare