Are multi-line equations not supported by the WP Latex plug-in?

I tried to write the example given at http://elevatorlady.ca/doc/refcard/expressions.html:

`\begin{split}\tan^2 x`

&= \sin^2 x/\cos^2 x \\

&= 1/\cos^2 x - 1

\end{split}

But all I get is an ugly "Formula does not parse". If I remove the \begin, \end and the & signs, it parses correctly. What is going on? I wrote it in the post like this:

`[latex]\begin{split}\tan^2 x &= \sin^2 x/\cos^2 x &= 1/\cos^2 x - 1\end{split}[/latex]`