Is there a circle symbol?

Is there a circle symbol for the composition of two functions? Or do I have to resort to using other ways to represent that?

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just as a tip, Wikipedia uses LaTeX style markup for their functions. When your press the edit button you can see :[itex](f\circ f)(x) = f(f(x)) = f^2(x)</math> ;) –  Davy Landman Jan 5 '11 at 8:43

\documentclass{article}
\usepackage{fixltx2e} % To make $$...$$ robust
\begin{document}
$$f \circ f$$
\end{document}

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Ah thanks, but just \circ would have done :) –  wrongusername Jan 5 '11 at 8:20
@wrongusername. Yes, but it's generally considered a good idea to post something compilable. This one was not exactly hard :-) –  Joseph Wright Jan 5 '11 at 8:25
I'm a bad illustrator, but for me, after drawing the circle, \circ was the first hit.