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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.

\begin{equation}
  \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.

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

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


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