My favorite theorem is $ \sum^n_{i=0}i=\frac{n(n+1)}{2} $. I like this theorem not as much for it's importance but because of the story behind it. The story I've heard is that when Gauss was a young boy, his teacher made every student sum all the numbers from 1 to 100 to keep them occupied. Gauss however was able to return the correct answer in a matter of seconds, and when his teacher asked him how he was doing it, Gauss showed him how he had derived this useful equation.--Jniederh 22:35, 24 January 2009
