tren may phang chua 4 duong thang bat ki do lay 1 diem O bat ki .qua O ke cac duong thang song song voi 4 duong thang da cho.tai O co 8 goc doi 1 doi dinh co tong bang 360 do.==>chac chan co 1 goc tao boi 2 duong thang bat ki <60 (360/8=45)
tren may phang chua 4 duong thang bat ki do lay 1 diem O bat ki .qua O ke cac duong thang song song voi 4 duong thang da cho.tai O co 8 goc doi 1 doi dinh co tong bang 360 do.==>dieu phai c/m