[SOLVED] Pythagoras theorem

okay, ive got a big square, with a square inside it diagonally. leaving 4 right angled triangles. one at each cornor of the large square.

sides of the internal squares are 'z' and the 3 sides of triangle are x y and z.. z is the hypotenuse...

i have shown that the large square's area can be written as (x+y) squared and also as z squared + 2xy.

now i have to use these results to prove pythagoras theorum?!?! :mad:

can any1 help with that? like now.. lol i have to give it in 2moro at skool.