cho tam giac abc can tai a co goc a bang 30 do tren nua mat phang bo ba khong chua diem c ve bx vuong goc voi ab lay diem n thuoc bx sao cho bn bang ba ve tam giac bcm deu.cmr:a,tam giac mab bang tam giac mac
b,tam giac cnb bang tam giac mab
c,tinh goc bcn