math-arc.sty

\ProvidesPackage{math-arc}  % 表示曲线弧

\RequirePackage{tipa}
\RequirePackage{graphicx}

\makeatletter
\DeclareFontFamily{U}{tipa}{}
\DeclareFontShape{U}{tipa}{m}{n}{<->tipa10}{}
\newcommand{\arc@char}{{\usefont{U}{tipa}{m}{n}\symbol{62}}}%

\newcommand{\Arc}[1]{\mathpalette\arc@arc{#1}}
\newcommand{\arc@arc}[2]{%
  \sbox0{$\m@th#1#2$}%
  \vbox{%
    \hbox{\resizebox{\wd0}{\height}{\arc@char}}%
    \nointerlineskip%
    \box0%
  }%
}
\makeatother