\appendix
# Needs \usepackage{appendix}
\appendixpage
\addappheadtotoc

* This is appendix A

  Definition of psedorapidity.

  #+begin_src latex
    \begin{equation}
    \label{eq:eta}
    \eta = -\ln\Bigg[\tan\Bigg(\frac{\theta}{2}\Bigg)\Bigg]
    \end{equation}
  #+end_src