# [OS X TeX] brace spanning equations

Samuel Lelievre samuel.lelievre at univ-rennes1.fr
Tue Mar 21 08:28:09 EST 2006

You could use the "cases" macro as in the following
(found in Herbert Voss's paper "Farbige Mathematik").

\begin{align}\label{eq:3}
\frac{I(\alpha )}{I_{0}}=%
\begin{cases}
\sqrt{1-\frac{\alpha}{\pi}+\frac{1}{2\pi}\sin 2\
alpha}
& \varphi =0\\[0.4cm]
\sqrt{2\left(1-\frac{\alpha}{\pi}\right)\left(2+%
\cos 2\alpha \right)+\frac{3}{\pi}\sin 2\alpha}
& \varphi =\frac{\pi}{2}
\end{cases}
\end{align}

Another solution is to use an array in between
"\left\{" and "\right." (where "\right." produces
an empty right delimiter).
You need that because each \left delimiter
must have a matching \right delimiter (although
the delimiters themselves may be different).
(says Michael Doob's "gentle introduction to latex",
which gives as exercise 5.30 "use a matrix construction
to typeset ...", and comments "this exercise and more
general constructions of this type may also be typeset
with the \cases macro". A margin notes refers to
TeXbook: 175.)

Best wishes
Samuel Lelievre

>I still have not solved this for myself. What is the magic command?
>
>Thanks.
>
>George Dorner
>
>
>On Mar 15, 2006, at 4:48 PM, KL Tah wrote:
>
>>hi all,
>>
>>sorry if this is elementary by i couldn't find an answer to  this on the web.
>>what's the control sequence to have a vertical brace spanning several equations?
>>
>>cheers,
>>kl
>>
>>
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>
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& FAQ: http://latex.yauh.de/faq/
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