设DE＝x AD＝y因为AF＝AD＝y EF=DE=x tan∠EFC=3/4 所以EC=3x/5 FC=4x/5 BF=y-4x/5 ∴ΔEFC∽ΔFAB 得EF/AF=EC/BF ∴x/y=(3x/5)/(y-4x/5) ∴y=2x,代入x^2+y^2=125 x=5,y=10 周长为2(y+3x/5+4x/5)=36 cm
