Euclid's proof diagram for the Pythagorean theorem.
The area of square ACFG is equals to the area of rectangle CJKE.
Click the play button at left below corner of the graphics view, equal area transits as {Area of square ACFG}/2={ΔACF}⇒{ΔBCF}⇒{ΔACE}⇒{ΔCEJ}={Area of rectangle CJKE}/2.
Similarly the area of square BAHI is equals to the area of rectangle BDKJ.