Error changing font in equation

I am trying to change fonts in an equation. It worked in another document compiled with XeLaTeX, but for some reason I get an error message if I remove the % before the setmathsfont. What am I missing:

documentclass[11pt]{article}
usepackage[inner=1.125in, outer=1in, top=1in, bottom=1in]{geometry}  
usepackage{amssymb}
usepackage{blindtext}
usepackage[math]{mathspec}
defaultfontfeatures{Mapping=tex-text}


setromanfont[Mapping=tex-text]{Minion Pro}
setsansfont[Scale=MatchLowercase,Mapping=tex-text]{DTL Caspari TOT Medium}
%setmathsfont(Digits,Latin,Greek)[Numbers={Lining,Proportional}]{Minion Pro}



begin{document}
section*{Calculus Formulas}
$int{u^n , du} = frac{u^{n+1}}{n+1}$[.5em]
$int frac{du}{u}=ln |u|+c$[.5em]
$int sin(u) , du=-cos(u)+c$[.5em]
$int cos(u) , du=sin(u)+c$[.5em]
$int sec^2(u) , du=tan(u)+c$[.5em]
$int csc^2(u) , du=-cot(u)+c$[.5em]
$int sec(u) tan(u) . du=sec(u)+c$[1em]
$e^x=1+x+frac{x^2}{2!}+frac{x^3}{3!}+ frac{x^4}{4!}+ dots + frac{x^n}{n!} + dots$

end{document}