\documentclass{minimal}
\textwidth=3.2in
\usepackage{amsmath}
\usepackage{fontspec} % requires xelatex or lualatex
\usepackage{unicode-math}
% this is a system font: use fontname, not filename
\setmainfont{Cambria}
\setmathfont{Cambria Math}

\begin{document}
\input{math_inc}
\end{document}

