[OS X TeX] set difference using TikZ and beamer

[Art Werschulz]

Hi.

I'm trying to do a slide that contains a Venn diagram and some  
commentary.  I found Til's Venn diagram example at
	http://www.texample.net/tikz/examples/venn-diagram
and I'm trying to somewhat blindly modify same.

Here's the code for such a page:

<snip>
\doocumentclass{beamer}

\usepackage{tikz}
\usetikzlibrary{shapes,backgrounds}

\usepackage{comment}

\begin{document}
\pagestyle{empty}

\begin{frame}
   \frametitle{Constructing $C$}
   \begin{center}
     \begin{tikzpicture}
       \newcommand\circleA{(0,0) circle (1.5cm)}
       \newcommand\circleB{(2cm,0) circle (1.5cm)}
       \begin{scope}[even odd rule]% first circle without the second
         \clip \circleB (-2,-2) rectangle (2,2);
         \fill[yellow] \circleA;
       \end{scope}
       \begin{scope}[even odd rule]% second circle without the first
         \clip \circleA (-2,-2) rectangle (4,4);
         \fill[yellow] \circleB;
       \end{scope}
       \draw \circleA node {$L(A)$};
       \draw \circleB node {$L(B)$};
     \end{tikzpicture}
   \end{center}
   \[L(C) =
   \big(L(A)\cap\overline{L(B)}\big) \cup \big(L(B)\cap\overline{L(A)} 
\big).\]
   \begin{itemize}
      \item We used proofs by construction to show that regular
        languages are closed under union, intersection, and complement.
      \item We can use those constructions to construct a~FA that
        accepts~$L(C)$.
   \end{itemize}
\end{frame}

\end{document}
</snip>

Unfortunately, the diagram starts way too low on the page.  As a  
result, the last two lines of text don't appear on the slide.

Any ideas on how to fix?  Thanks.

Art Werschulz (8-{)}   "Metaphors be with you."  -- bumper sticker
GCS/M (GAT): d? -p+ c++ l u+(-) e--- m* s n+ h f g+ w+ t++ r- y?
Internet: agw STRUDEL comcast.net