Spotlight has a useful calculator good for simple arithmetic. It will also return several constants, including pi and e.
Perhaps as a joke, it will also return pie (pi*e) = 8.5397342227 from the Calculator application.
[crarko adds: OK, I admit it's not much of a hint, but I do appreciate the fact that somebody at Apple has a sense of mathematical humor. And I'm posting several small things from the queue today. Happy December 1st.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=2010110912243532