cho tam giac ABC vuong tai A , goi I la trung diem cua canh AC .tren tia doi cua tia IB lay diem D sao cho IB bang Id . chung minh
a CID bang AIB , b AD bang BC , ADsong song BC C , goi Mva N lan luot la trung diem AD va BC . chung minh M,N,I thang hang