Inline math tests (mathjax plugin)
This is is a test: $a^2 + b^2 = c^2$
This is another test: \(1+2+\dots+n=\frac{n(n+1)}{2}\)

To display math on its own line, use double dollar signs:
⇒ $$  frac{d}{dx} left(  int_{0}^{x} f(u) ,du right)=f(x) $$
gives: $$ \frac{d}{dx}\left( \int_{0}^{x} f(u)\,du\right)=f(x) $$

or escaped square brackets:
⇒  [  sin A  cos B =  frac{1}{2} left[  sin(A-B)+ sin(A+B)  right]  ]
gives: \[ \sin A \cos B = \frac{1}{2}\left[ \sin(A-B)+\sin(A+B) \right] \]

Numbered equations:

          If $\hat T_p$ is the complex fourier tranform, the bispectrum (triple correlation) is: \begin{equation} \hat T_{p,q}^{(3)}=\hat T_p.\hat T_q. \hat T_{-p-q} \end{equation}