How do I turn off equation auto numbering

Question

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{align}

For some reason, LaTeX is automatically labeling the equation. How do I turn that off? Secondly how do I write something in LaTeX on this site. I tried enclosing in '$' but it doesn't work.

Answer 1

Do a \begin{align*} ... \end{align*}. That should do the trick.

Answer 2

If you only want some of the lines in an align environment to not be numbered, just put \nonumber before the end characters on each of the lines you don't want to have numbers. Otherwise, use align* as JCL suggested so that none of the lines will be numbered.

Answer 3

As a sidenote, the mathtools package, which makes some improvements on amsmath, provides a way of labeling only those equations that are referenced in the text.

\documentclass{article}  
\usepackage{mathtools}  
\mathtoolsset{showonlyrefs}  
\begin{document}  
\begin{gather}  
  a = b \label{eq1} \\  
  c = d \label{eq2}  
\end{gather}  
Some text, \eqref{eq2}.  
\end{document}

In this case, only the second of the equations, c = d, is numbered, as that is the only one being referenced in the text.

Notes

• three compiler passes are required for the references to show up properly
• this does not work with cleveref, but the cleveref manual mentions another package, autonum, that performs the same task, yet is compatible with cleveref.
• the manual of the present version (dated 2012/05/10) notes two bugs, one can cause that the number is printed close to, or on top of, the equation, the other relates to ntheorem. Refer to the manual for details.

Answer 4

If you use this:

\begin{equation}
...
\end{equation}

try this instead:

\begin{equation*}
...
\end{equation*}

This solution requires the use of the package amsmath.

Answer 5

Note whilst the above answers are relevant to the question, a lot of people include equations in LaTeX using the \begin{equation} which works without explicitly including the amsmath package in a LaTeX document. However when one attempts to the use \begin{equation*} directive (to omit numbering) an error is generated. Thus in this case it should be pointed out that one needs to explicitly import the amsmath package:

\usepackage{amsmath}

Answer 6

"\nonumber" sometimes does not work for me. Another possibility is to do:

\begin{center}
$ 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{center}

Answer 7

\documentclass{article}
\usepackage{amsmath}
\begin{document}
  Solve these problems
  \begin{align*}
  1. \;\; &   x= y+z & 2.\;\; &x^n= y^n+z^n \\  
   3.\;\; &  x= y+z &  4.\;\;  & x^n= y^n+z^n \\ 
    \end{align*}

    {\bf  This is some sample text we will use to create a somewhat longer text
        spanning a few lines.}

        \begin{align*}
   5.\;\; &  x= y+z & 6.\;\; & x^n= y^n+z^n\\   
  \end{align*}
\end{document}

This gives required output.