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How can I write an equation with one curly brace ({), and on the right-hand side next to the curly, two statements in two different lines?

Nikos Hidalgo
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y2p
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    Why is this question in stackoverflow rather than in tex.stackexchange ? Though it is answered there: http://tex.stackexchange.com/questions/9065/large-braces-for-specifying-values-of-variables-by-condition – Vincent Fourmond Jan 15 '17 at 14:28

6 Answers6

232

You can try the cases env in amsmath.

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{equation}
  f(x)=\begin{cases}
    1, & \text{if $x<0$}.\\
    0, & \text{otherwise}.
  \end{cases}
\end{equation}

\end{document}

amsmath cases

Tombart
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Lachezar
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    @Lucho Is it possible to have two different numbers to these two equations on the right? – MLT Jan 07 '14 at 15:23
26

That can be achieve in plain LaTeX without any specific package.

\documentclass{article}
\begin{document}
This is your only binary choices
\begin{math}
  \left\{
    \begin{array}{l}
      0\\
      1
    \end{array}
  \right.
\end{math}
\end{document}

This code produces something which looks what you seems to need.

curly braces in front of two lines

The same example as in the @Tombart can be obtained with similar code.

\documentclass{article}

\begin{document}

\begin{math}
  f(x)=\left\{
    \begin{array}{ll}
      1, & \mbox{if $x<0$}.\\
      0, & \mbox{otherwise}.
    \end{array}
  \right.
\end{math}

\end{document}

This code produces very similar results.

enter image description here

Bruno BEAUFILS
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    This solution gives an output identycal to the `cases` environment of `amsmath`, except for a slightly smaller curly brace, which sometimes can be an advantage. – mmj Jan 27 '16 at 10:44
8

To answer also to the comment by @MLT, there is an alternative to the standard cases environment, not too sophisticated really, with both lines numbered. This code:

\documentclass{article}
\usepackage{amsmath}
\usepackage{cases}

\begin{document}

\begin{numcases}{f(x)=}
  1, & if $x<0$\\
  0, & otherwise
\end{numcases}

\end{document}

produces

screenshot of output pdf

Notice that here, math must be delimited by \(...\) or $...$, at least on the right of & in each line (reference).

MattAllegro
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8

Are you looking for 

\begin{cases}
  math text
\end{cases}

It wasn't very clear from the description. But may be this is what you are looking for http://en.wikipedia.org/wiki/Help:Displaying_a_formula#Continuation_and_cases

srean
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  • As @Lucho indicated you need \usepackage{amsmath}, but I assume you are using it anyways. The packages amsmath, amssymb and amsthm are hard to do without when typesetting math. – srean Oct 26 '10 at 20:10
0

Or this:

f(x)=\begin{cases}
0, & -\pi\leqslant x <0\\
\pi, & 0 \leqslant x \leqslant +\pi
\end{cases}
A-Sharabiani
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0

Here is a way to manually control the size of brace, if cases or \left\{ doesn't provide suitable brace size you want.

\begin{math}
    \biggl\{
        \begin{array}{l}
            statement1\\
            statement2
        \end{array}
\end{math}

You can choose among \bigl\{ \Bigl\{ \biggl\{ \Biggl\{ to adjust brace size from the smallest to the largest.

Image of different braces

From left to right: cases \left\{ biggl\{ Bigl\{

William
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