If this is for the Pythagorean Theorem where h is the hypotenuse, p is the perpendicular leg, and b is the base leg, most commonly stated as
, then there are literally dozens and dozens of proofs. I attach a screenshot from Alexander Bogomolny's blog at UMass Boston. On this page alone (which you can find with a Google search), he has 54 different proofs of the Pythagorean Theorem! I bet you can write your own...