cho goc aob,tia phan giac ox cua goc aob.tren nua mat phang bo chua tia ob voi bo la duong thang oa ve tia oy sao cho goc aoy>aob
a,chung to rang tia ob nam giua 2 tia oa va oy
b,tinh goc xoy biet goc yoa nam giua 2 tia oa va oy
c,chung to goc xoy=1/2(goc yoa+gocyob)
cac ban giup minh voi nha gap lam rui,cam on