A new friend surprised me. We were talking about the movie Pi (which I would be able to watch next February finally!) and he scribbled the math proof for Pi on a piece of paper, scanned it and emailed it to me. He needed it handwritten so he could use the math symbols. I think he did it off the top of his head rather than consult any math textbook. To quote him briefly, By experiments, we can cut a circle through the centre into N pieces of bilateral triangles. If N becomes larger, the circumference of the circle can be approximated by the summation of all opposite sides of the triangles.

Thank you, I think it's the first time I had a math proof as a Christmas gift. lol.