cho goc xoy=\(\delta\)\(\left(\delta<90^0\right)\)va M nam trong xoy.o ngoai xoy lay 2 diem E va F sao cho tia ox la trung truc cua ME. oy la trung truc cua MF
a) CM: OE=OF
b)Tinh goc EOF theo \(\delta\)
c) neu \(\delta=90^o\)thi O nam o dau tren EF .VI sao