This demonstration is often available in hands-on science museums. The problem I have is that it's just a demonstration for one particular right-angled triangle, not a proof in any sense.<p>See <a href="http://math.stackexchange.com/questions/675522/whats-the-intuition-behind-pythagoras-theorem" rel="nofollow">http://math.stackexchange.com/questions/675522/whats-the-int...</a> for examples of real proofs with insight.