Steven has already said enough, but just for completeness and for proving that LaTeX offers always new roads I'll post another solution by means of .., though I think cases
environment is the most appropriate for this job.
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
t(v) = \left\{\begin{array}{lr}
\text{John} & \text{hvis $v$ er variabelen $x$}\\
\text{Paul} & \text{hvis $v$ er variabelen $y$}\\
\text{George} & \text{hvis $v$ er variabelen $z$}\\
\text{Yoko} & \text{ellers}
\end{array}\right.
\]
\end{document}
This produces

Notice that amsmath
package is only needed for text command
. A benefit from using array
would be that you can control alignment by means of r
and l
(respectively right aligned, and left aligned) arguments in \begin{array}{lr}
, and you can add lines as well as control manually spacing, by writing
\[
t(v) = \left\{\begin{array}{l@{\hspace{3em}}|r}
\text{John} & \text{hvis $v$ er variabelen $x$}\\
\hline
\text{Paul} & \text{hvis $v$ er variabelen $y$}\\
\text{George} & \text{hvis $v$ er variabelen $z$}\\
\text{Yoko} & \text{ellers}
\end{array}\right.
\]
@{\hspace{3em}}
can be set to whichever value in em
, cm
, pt
and other measure you like for making custom space between columns, while |
can be used for adding vertical lines bewreen the arry columns. Finally adding \hline
you can achieve horizontal rules.
Little addendum: \left\{
and \right.
fake the case behaviour of cases
environment, so that if you prefer you can switch it to othe parenthesis, as [
, (
, \langle
and so on.