That's what comes to mind when someone asks what the Pythagorean Theorem is. Simply put 'The hypotenuse of a right triangle is the side opposite the right angle', sometimes referred to by students as the long side of the triangle. The other 2 sides are referred to as the legs of the triangle. The theorem states that the square of the hypotenuse is the sum of the squares of the legs. In this image, the legs would be the sides of the triangle where A and B are. The hypotenuse is the side of the triangle where C is. Always understand that the Pythagorean Theorem relates the areas of squares on the sides of the right triangle. To see the application of the theorem, select 'next'.