答案1
试用包mathtools
\documentclass{article}
\usepackage{mathtools}
\begin{document}
$\xleftrightarrow[\text{world}]{\text{hello}}$
\end{document}
试用包mathtools
\documentclass{article}
\usepackage{mathtools}
\begin{document}
$\xleftrightarrow[\text{world}]{\text{hello}}$
\end{document}