Cómo poner $f(x)=\begin{cases}1, &|x| \le 1,\\ 0, &|x|>1. \end{cases}$ en contenido?

Question

\documentclass[18pt,a4paper]{article}

...


\tableofcontents

...

\subsection{$f(x)=\begin{cases}1, &|x| \le 1,\\ 0, &|x|>1. \end{cases}$}

Lo compilo, TeXstudio me da error:

"Falta \endcsname insertado. \end{cases}$ }"

¿Cómo plasmar la fórmula en contenido?

Answer 1

\documentclass[a4paper, 12pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}

\begin{document}

\tableofcontents

\section{$f(x) = \protect\begin{cases} 2 & \vert x \vert < 3 \\ -5 & \vert x \vert > 4 \protect\end{cases}$}

\subsection{$f(x) = \protect\begin{cases} 1 & \vert x \vert < 1 \\ 0 & \vert x \vert > 1 \protect\end{cases}$}


\end{document}