As can be seen from the figure11-kloc-0/8, except the two right-angled triangles in the figure117, all the other triangles are right-angled isosceles triangles.

The trapezoidal area is (a+b)/2 * (a+b) = (a+b) 2/2. Subtract two original right-angled triangles, and the area of the other triangle is (A 2+B 2)/2, which is directly C 2/2 according to the side length of the other triangle. In this way, we can get A 2+B 2 = C 2, which verifies the Pythagorean theorem.