147

This question already has an answer here:

I want to write a conditional expression such as the following.

enter image description here

What is the best way to express such conditional expressions in Latex?

marked as duplicate by Werner, user13907, Martin Schröder, Heiko Oberdiek, Paul Gaborit Jun 18 '15 at 6:07

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • 2
    use cases or dcases. – Peter Grill Mar 7 '12 at 20:05
188

I think this is a job for cases from the amsmath package

enter image description here

\documentclass{article}
\usepackage{amsmath}

\begin{document}
\[
    f(x)= 
\begin{cases}
    \frac{x^2-x}{x},& \text{if } x\geq 1\\
    0,              & \text{otherwise}
\end{cases}
\]
\end{document}

or if you would prefer a displaystyle fraction, then you could use dcases from the mathtools package, which extends (and loads) the amsmath package.

enter image description here

\documentclass{article}
\usepackage{mathtools}

\begin{document}
\[
    f(x)= 
\begin{dcases}
    \frac{x^2-x}{x},& \text{if } x\geq 1\\
    0,              & \text{otherwise}
\end{dcases}
\]
\end{document}
  • I had thought you usually want a \, before text punctuation inline with math, no? – Doctor Mohawk Sep 12 '17 at 14:56
  • Is it possible to change the curly braces to bracket in this environment? – H. R. Sep 19 '17 at 7:31
33

Just for the sake of completeness: There is a pseudo-parenthesis . that can be used to terminate an opening parenthesis:

\documentclass{standalone}

\begin{document}
$\left\{a+b=c\right.$
\end{document}

Output: Result of compilation

  • 5
    You should expand this answer to show how to use this to produce the output in the original image. – Peter Grill Mar 10 '12 at 1:04
  • 4
    @PeterGrill: Well, there are ways, but cases and dcases are much much more suitable for this task. Are there conditions where these environments are not available? – krlmlr Mar 10 '12 at 5:48
  • 2
    I actually like your answer better. – 0rkan Sep 25 '15 at 3:09
  • I like this answer for its flexibility. It shows how to create a single-sided brace (or any other grouping symbol) for applications where cases isn't suitable. – drmuelr Oct 13 '18 at 5:31

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