Who was Pythagoras, and what did he do?

Some attribute this golden world knowledge to Plato, others to Pythagoras.

And this kind of proof is the kind of proof that you need to learn when you're learning mathematics in order to get an idea of what it means before you look into the, literally, 1,200 or 1,500 proofs of Pythagoras' theorem that have been discovered.

So a more direct one, one that gives you more of the feeling of math, is something closer to Pythagoras' own proof, which goes like this so here we have this triangle, and if we surround that C square with three more triangles and we copy that, notice that we can move those triangles down like this.