The Pythagorean Theorem states: In any right triangle, the area of the square whose side is the hypotenuse (the side opposite the right angle) is equal to the sum of the areas of the squares whose sides are the two legs (the two sides that meet at a right angle).
The Pythagorean theorem can be written as an equation relating the lengths of the sides a, b and c, often called the Pythagorean equation: