Rút gọn M = sin(x - y)cosy + cos(x - y)siny, Rút gọn: M = sin(x – y)cosy + cos(x – y)siny., Rút gọn M = sin(x – y)cosy + cos(x – y)siny, Rút gọn M = sin(x – y)cosy + cos(x – y)siny.