Proof 3.7c

Proof: Consider a right (Definition 21) where the right angle is at . Place a right triangle at each side on each side of the triangle so that the side lengths of the triangle are the side lengths of the legs of the triangles respectively. The area of each of these triangles are expressed by  where b and h are the lengths of the triangles' legs. The area of the triangles would then be considered  where a is  and  where b is . According to