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#### 16.7.4 \left & \right

Synopsis:

\left delimiter1 ... \right delimiter2


Make matching parentheses, braces, or other delimiters. The delimiters are sized according to the math they enclose. This makes a unit vector surrounded by appropriate-height parentheses.


\left(\begin{array}{c}
1   \\
0   \\
\end{array}\right)


Every \left must have a matching \right. Leaving out the \left( in the above gets ‘Extra \right’. Leaving off the \right) gets ‘You can't use \eqno' in math mode’.

However, the two delimiters delimiter1 and delimiter2 need not match. A common case is that you want an unmatched brace, as below. Use a period, ‘.’, as a null delimiter.

$$f(n)=\left\{\begin{array}{ll} 1 &\mbox{--if $$n=0$$} \\ f(n-1)+3n^2 &\mbox{--else} \end{array}\right.$$


Note that to get a curly brace as a delimiter you must prefix it with a backslash, \{`.