Pythagoras' Theorem states that in a right angled triangle, the square of the hypotenuse (the long side) is equal to the sum of the squares of the other two sides.

It can be written as the formula

This theorem is attributed to Pythagoras, a Greek mathematician and philosopher who founded a cult that studied mathematics and music. This cult had a number of interesting rules, such as never eating beans and never touching a white rooster. However, some Babylonian tablets over a thousand years before Pythagoras' time suggest that the ancient Babylonians had some knowledge of this theorem.