Similarly,
∴△FMN∽△ABC
D and e are the midpoint of AB and AC respectively. According to the similarity ratio,
∴S= 1/9
(2) The D-crossing point is DH∨BE, and the AC-crossing point is H.
By substitution: FM/AB=2/9
△FMN∽△ABC from ( 1)
S=4/8 1
(3) the square of s =1(A+B+ 1)