For example, let us say that I want to use macro to typeset matrices. Just in case I later decide that I want to somehow change how they look, I can then change it in one place - in this macro.
MathJax Documentation says that \newenvironment works. But if I try the same syntax I use in TeX, it does not seem to work.
Example:
$\newenvironment{mymatrix}{\left(\begin{smallmatrix}}{\end{smallmatrix}\right)}\begin{mymatrix}a&b\\-b&a\end{mymatrix}$ does not work
$\left(\begin{smallmatrix}a&b\\-b&a\end{smallmatrix}\right)$ works
$\newenvironment{mymatrix}{\left(\begin{smallmatrix}}{\end{smallmatrix}\right)}\begin{mymatrix}a&b\\-b&a\end{mymatrix}$ does not work
$\left(\begin{smallmatrix}a&b\\-b&a\end{smallmatrix}\right)$ works