# Unable to use bmatrix

I can create a matrix in parentheses:

$$\pmatrix{5 & 6 \\ 5 & 6}$$

but not in square brackets

I can create a matrix in parentheses:

$$\bmatrix{5 & 6 \\ 5 & 6}$$

Why is \bmatrix missing on StackExchange?

$$\begin{bmatrix}5 & 6 \\ 5 & 6\end{bmatrix}$$
$$\begin{bmatrix}5 & 6 \\ 5 & 6\end{bmatrix}$$
• \pmatrix is defined in Plain TeX, but \bmatrix is not, and it is not part of the AMSmath package on which MathJax is based. You can, of course use \def\bmatrix#1{\begin{bmatrix}#1\end{bmatrix}} to define it if you want. – Davide Cervone Feb 24 '16 at 13:47