How would you define the Pythagoras Theorem?

It is difficult to better the definition given originally. The Pythagorean theorem states that the sum of the squares on the sides of a right triangle equals the square of the hypotenuse. These words may not mean much to many people. It is much easier to see it in a demonstration.

Liu Hui proved the theorem by cutting a2 and b2, the squares on the sides, into various shapes that can be rearranged to form c2, the square of the hypotenuse. When you see such a demonstration, the theorem makes sense and you are more likely to remember it.