cho tam giac abc can tai a duong cao ah tren tia ac lay diem m sao cho ac bang cm.keo dai ah cat bm tai e
a, cmr hb bang hc
b,cmr tam giac ebc can
c,hai dg thang ab va ce cat nhau tai k.cmr.e la trong tam cua tam giac akm
d,cmr..am - ab lon hon em - eb