Pythagorean theorem proof (with leg rule)
In the applet below we have the right triangle ABC and we apply the leg rule: the steps show how to prove that the square on each leg is equivalent to the corresponding rectangle whose sides are the hypotenuse and the projection of the leg on it.
So if each square is equivalent to the corresponding rectangle ( and )
the sum of the squares is equivalent to the sum of rectangles
As you can see, the two rectangles together make the square on the hypotenuse .