Insert some Latex code in a question [duplicate]

Possible Duplicate:
Latex in Stack Overflow?

In many sites of the Stack Exchange network there is the possibility to insert some Latex code directly in your question (i.e. MathJaX equations $\sin^2 \theta$).

I tried this on SO but the result wasn't as expected.

What is, if exists, the command for inserting a complex equation in Latex?

E.g.

z = \sum_{k=1}^{|{\cal N}l|} \alpha{k}e^{-\frac{\left\| (\Bxs,\Bys) - \mu_k(\Bxs,\Bys) \right\|^2}{2{\sigma_k(\Bxs,\Bys)^2} } }

If not existing, do you think it could be a useful feature?