cho tam giac ABC khong can co AD la phan giac.tren tia doi tai BA lay E.tren tia doi tia CA lay E sao cho BE=BC=CF,BF cat CE o I.Duong thang qua I song song AD cat AC o K,duong thang qua c song song voi AB cat nhau o P
b,cm BF,CE la pgiac cac goc CBP va BCP
c,o la giao diem cua AD va BP.cm PI song song AO
d,cm AB=CK
