7.55.2 Greatest hits from previous weeks

7.55.2.1 Show equation number only once in align environment

https://tex.stackexchange.com/landing/r/digest?cta=question&id=17528

I want the equation number to be shown only at the last line, or better, somewhere in the middle of all. So instead of (1), (2), ... only (1). 
I use \begin{align} ... \end{align} 
[equations] [align]
 

asked by Theta30 https://tex.stackexchange.com/landing/r/digest?cta=user&id=5350 226 votes

7.55.2.2 What is the "correct" way of embedding text into math mode?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=3415

Lets say I have something like: 
\[ Let x = number of cats \] 
(This is a contrived example, but pretend we are actually inside a long align environment block...) "Let" and "number of cats" need to ... 
[math-mode]
 

asked by Billy ONeal https://tex.stackexchange.com/landing/r/digest?cta=user&id=192 255 votes

7.55.2.3 How do I change the `enumerate` list format to use letters instead of the default Arabic numerals?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=2291

I've seen documentation whereby an \alph command is put around the \begin{enumerate} somewhere, but I'm not entirely sure how that operates... 
[numbering] [lists] [enumerate]
 

asked by Billy ONeal https://tex.stackexchange.com/landing/r/digest?cta=user&id=192 368 votes

answered by frabjous https://tex.stackexchange.com/landing/r/digest?cta=user&id=411 322 votes

7.55.2.4 How do I turn off equation auto numbering

https://tex.stackexchange.com/landing/r/digest?cta=question&id=2597

I have an equation like this: 
\begin{align} 
P(A \cup B) = \sum_{\omega \in A \cup B} P(\omega) = \sum_{\omega \in A} P(\omega) + \sum_{\omega \in B} P(\omega) 
= P(A) + P(B) 
\end{... 
[equations] [numbering]
 

asked by user1046 https://tex.stackexchange.com/landing/r/digest?cta=user&id=1046 162 votes

answered by levesque https://tex.stackexchange.com/landing/r/digest?cta=user&id=10 183 votes

7.55.2.5 Using the \tab Command

https://tex.stackexchange.com/landing/r/digest?cta=question&id=198432

I have seen several cases of people using the \tab command to insert a specific amount of space between objects (as opposed to the \hfill command which uses any remaining space).  However, I have ... 
[spacing]
 

asked by Mathematician https://tex.stackexchange.com/landing/r/digest?cta=user&id=49199 77 votes

answered by Mathematician https://tex.stackexchange.com/landing/r/digest?cta=user&id=49199 89 votes

7.55.2.6 How to write two dot above a letter?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=152951

the two dots above a letter represents two derivative of varible t. 
My method: 
\documentclass[UTF8]{ctexart} 
\usepackage{amsmath} 
\usepackage{amssymb} 
\usepackage{graphicx} 
\usepackage{epstopdf} 
\... 
[math-mode] [accents]
 

asked by mma https://tex.stackexchange.com/landing/r/digest?cta=user&id=43727 117 votes

answered by Cain https://tex.stackexchange.com/landing/r/digest?cta=user&id=28428 162 votes

7.55.2.7 Absolute Value Symbols

https://tex.stackexchange.com/landing/r/digest?cta=question&id=43008

What is the "best LaTeX practices" for writing absolute value symbols?  Are there any packages which provide good methods? 
Some options include|x| and \mid x \mid, but I'm not sure which is best... 
[math-mode] [symbols]
 

asked by jamaicanworm https://tex.stackexchange.com/landing/r/digest?cta=user&id=9757 293 votes

answered by Peter Grill https://tex.stackexchange.com/landing/r/digest?cta=user&id=4301 218 votes