cho tam giác abc nhọn ab=4.5 ,ac=6, bc =7.5 m thuoc ab, am=3 ,n thuoc ac, an= 4
a) CM mn song song bc
b)tinh mn
c) ke duong phan giac ae , e thuoc bc , bh va ck vuong goc voi ae CM ah.ec=be.ak
d) lay i thuoc ak sao cho goc bae = gocbci CM ae^2=ab.ac-eb.ec