25

I would like to put a tall (long) left curly bracket on the left side of the following:

\documentclass[12pt]{article}

\begin{document}

\noindent
c: $\{$1, ..., n$\}$ $\rightarrow$ $\{$1, ..., n$\}$, such that

\hspace{20 mm}

\noindent
c($a_i$) = $a_{i+1}$ for 1 $\le$ $i$ < $l$

\hspace{20 mm}

\noindent
c($a_l$) = $a_1$


\end{document}

Please let me know if you can help. Thanks!

32

The following may be close to what you're looking for:

enter image description here

\documentclass[12pt]{article}
\usepackage{amsmath}
\begin{document}
\begin{gather*}
c \colon \{1, \dots, n\} \rightarrow \{1, \dots, n\} \text{ such that}\\    
\begin{cases}
  c(a_i) = a_{i+1} & \text{for }1\le i<l\\    
  c(a_l) = a_1    
\end{cases}
\end{gather*}
\end{document}

Some comments:

  • Use the cases environment, provided by the amsmath package, to place a left curly brace ahead of two or more expressions.
  • Don't use ...; use \dots instead to get a typographical "ellipsis".
  • Use the \text{ } command to write upright text inside mathematical expressions.
  • As pointed out in the comments by @SvendTveskæg and @daleif, it's better (typographically speaking) to use the command \colon instead of :.

On the other hand, if you need the left-hand curly brace to span all three rows, you could do so with the following code: enter image description here

\documentclass[12pt]{article}
\usepackage{amsmath}
\begin{document}
\begin{equation*}
\begin{cases}
  c \colon \{1, \dots, n\} \rightarrow \{1, \dots, n\} \text{ such that}\\      
  c(a_i) = a_{i+1}  \text{ for $1\le i<l$}\\
  c(a_l) = a_1
\end{cases}
\end{equation*}
\end{document}
|improve this answer|||||
  • 2
    For mappings, one should use \colon instead of : in order to get the correct spacing. – Svend Tveskæg May 17 '13 at 8:27
  • 2
    Most people don't, because they don't know about \colon. But I agree. – daleif May 17 '13 at 13:14
  • @SvendTveskæg and daleif - Thanks for this; I'll modify the examples. – Mico May 17 '13 at 13:26
  • 1
    Shouldn't you write \\ to skip line, e.g. right after such that ? – user130222 Apr 10 '17 at 17:02
  • 2
    @user130222 - Thanks for bringing the missing-double-backslash issue to my attention. There's been a most unfortunate site-wide software bug earlier this year, which "replaced" [!] lots and lots of (but weirdly not all) double-backslash instances with single-backslash instances. It's been a nightmare, honestly, to track down and fix all the postings affected by this bug. I hope it didn't trip you up too much. Again, thanks for bringing it to my attention; I've fixed the code (for now). – Mico Apr 10 '17 at 17:46
14

Although the cases environment probably suits your needs best, I'd like to mention the more versatile and (probably) equivalent syntax \left\{ <blank> \right\}for future use, in case you haven't come across it.

|improve this answer|||||
  • It is not necessarily more versatile and not equivalent. This has been discussed quite a few times on this site, you can read more say in this one as it popped up first in the search tex.stackexchange.com/questions/208284/… – percusse Aug 15 '15 at 16:35
  • The method you're proposing has rather different syntax from the cases environment. The latter is designed for typesetting left-hand (result) and right-hand (conditioning information) material in a unified way. To mimic the syntax and structure of the cases environment using your setup, it would be necessary to define an interior array (or equivalent) environment as well. – Mico Aug 15 '15 at 16:55
  • Thanks folks, you're both right. Since I've never used more than two 'cases', I guess I just assumed both methods were more or less equivalent. And of course I also forgot to mention the need of array. – Quaternion Aug 16 '15 at 10:55
  • 1
    +1 thanks for mentioning that. Not everyone on this site is a master at LaTeX. – BlueRaja - Danny Pflughoeft Jul 22 '16 at 20:41

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