Pythagoras is best known for this theorem that shows the relationship of the sides of a right triangle. The Pythagorean Theorem states that the sum of the squares of the legs of a right triangle is equal to the square of the hypotenuse. The hypotenuse is always the largest side of a right triangle, the side opposite the right angle. In the formula, a2 + b2 = c2, a and b are the legs of the right triangle and c is the hypotenuse. This formula shows the relationship between the sides a, b, and c.