Using MathJax

\[ \mathbf{X} = \mathbf{Z} \mathbf{P^\mathsf{T}} \]

\[\frac{1}{\left(1+\left(\frac{1}{1+\left(\frac{1}{1+2x}\right)}\right)\right)}\]

\begin{equation} E = mc^2 \end{equation}

\[\phi(z) = \frac{1}{1+e^{-z}}\] \[cross-entropy = \sum_i ylog(y')\]

math.stackexchange

all greek letters

MIT tutorial