How can I change the math font in slides class?

Question

I use the "slides" class to get full size equations for a presentation. (Yes, it needs to be in Powerpoint ;) )

However, I want to have the standard math font (like in the article class). There seems to be no option like serif for the beamer class. The reason, I'm not using the beamer class is that I get a "picture" just the size of my equation in Powerpoint with the slides class. With beamer or article, I get a bigger "picture" with a lot of white space around my equation.

Minimum example:

\documentclass{slides}\pagestyle{empty} 
\usepackage{amsmath}

\begin{document}  
\begin{equation*}  
\Omega 
\end{equation*} 
\end{document}

Answer 1

I just followed egreg's lead in his answer at What are all the font styles I can use in math mode?, which indicated how the LaTeX kernel sets up math fonts.

\documentclass{slides}\pagestyle{empty} 
\usepackage{amsmath}
\DeclareSymbolFontAlphabet{\mathrm}    {operators}
\DeclareSymbolFontAlphabet{\mathnormal}{letters}
\DeclareSymbolFontAlphabet{\mathcal}   {symbols}
\DeclareMathAlphabet      {\mathbf}{OT1}{cmr}{bx}{n}
\DeclareMathAlphabet      {\mathsf}{OT1}{cmss}{m}{n}
\DeclareMathAlphabet      {\mathit}{OT1}{cmr}{m}{it}
\DeclareMathAlphabet      {\mathtt}{OT1}{cmtt}{m}{n}

\DeclareSymbolFont{operators}   {OT1}{cmr} {m}{n}
\DeclareSymbolFont{letters}     {OML}{cmm} {m}{it}
\DeclareSymbolFont{symbols}     {OMS}{cmsy}{m}{n}

\begin{document}  
\begin{equation*}  
y = mx + b ~~~\omega\Omega \mathbf{\Omega}\mathit{\Omega} 
\end{equation*} 
\end{document}

Answer 2

Note: equation also has margins, so you really can't get much smaller.

\documentclass{article}
\usepackage{xspace,xcolor}
\usepackage[screen,nopanel]{pdfscreen}


\margins{0pt}{0pt}{0pt}{0pt}
\screensize{1in}{4in}
\backgroundcolor{lightgray}% to show margins

\begin{document}
\begin{equation}
A = \pi r^2
\end{equation}
\end{document}