cho tam giac ABC vuong tai A . Tia phan giac cua goc B cat canh AC tai E tren canh BC lay diem F sao cho BF = BA / a. chung minh : AE =EF / b. tren tia doi cua tia EF lay M sao cho EM = EC . Chung minh B,A,M thang hang / c. chung minh BE VUONG GOC MC
