内切圆直角三角形面积公式

内切圆半径r=(a+c-b)/2
s=ac/2
=2ac/4
=(b^2-a^2-c^2+2ac)/4
=[b^2-(a-c)^2]/4
=[b-(a-c)][b+(a-c)]/4
=[(c+b-a)/2][(a+b-c)/2]
=AE*EC