求（tan10°
求（tan10°-√ 3）*sin40°的值
（tan10°-√ 3）*sin40° =（sin10°-√3*cos10°)*sin40°/cos10° =2sin(10°-60°)*sin40°/cos10° =-2cos40°*sin40°/cos10° =-sin80°/cos10° =-cos10°/cos10°=-1