Proofs of Pythagoras's Theorem
a²+b² = c²

Proof 11
From Monday, July 31st to Sunday August 6th, 2000 in Makuhari, Tokyo, Japan, the International Conference on Mathematics Education (or ICME 9) took place. On the Saturday an exhibition was staged, called Mathematical Art in ICME 9. One exhibit was the rotating structure shown below. As it turned, liquid flowed from the largest square to fill up the two smaller squares, thus proving Pythagoras's theorem.