\documentclass[12pt,a4paper]{article}
\usepackage{amsmath}
\begin{document}
\listoffigures
\[
\{[\phi(t+h),p(t+h)]_2\}
\]
\begin{figure}[htb]
\centering
something here
\caption[math $x+y$ ]{math $\{[\phi(t+h),p(t+h)]_2\}$ }
% \caption[math $\{[\phi(t+h),p(t+h)]_2\}$ ]{math $\{[\phi(t+h),p(t+h)]_2\}$}
\end{figure}
\end{document}
I want to use a short caption for \listoffigures. However, the simple math expressions ($x+y$) can work. But a more complicated math expression like
\caption[math $\{[\phi(t+h),p(t+h)]_2\}$ ]{math $\{[\phi(t+h),p(t+h)]_2\}$}
does not work.
Am I misunderstanding something in typing math using latex?
{$math$}LaTeX can't know here that the closing bracket in your formulae is not closing the optional argument. – Johannes_B Jan 14 '15 at 15:52]inside an optional argument – barbara beeton Jan 14 '15 at 16:01