試解
(10+x)^2+40^2=(30+x)^2
x=20, so sin a = 3/5, cos a= 4/5, tan a= 3/4
Angle G = a, so DG=40*4/3
MG = DG-20=160/3-20
MF=MG*3/5=20
(10+x)^2+40^2=(30+x)^2
x=20, so sin a = 3/5, cos a= 4/5, tan a= 3/4
Angle G = a, so DG=40*4/3
MG = DG-20=160/3-20
MF=MG*3/5=20