# Brace and Array with \frac and \cos, Height [duplicate]

Possible Duplicate:
Using display style fraction in a matrix environment

How do I create a left brace for an array such that it surrounds all the elements of the array? This is happening whenever one of the elements is \cos with \frac as its mandatory argument.

Minimal Working Example:

\documentclass{article}

\usepackage{amsmath}

\begin{document}
\begin{equation*}
\mathbf{A} = \frac{1}{\sqrt{\frac{n}{2}}} \left[
\begin{array}{c}
1 \\
\cos\frac{2\pi}{n} \\
\vdots \\
\cos\frac{2\pi(n-1)}{n}
\end{array}
\right.
\end{equation*}
\end{document}


Thanks.