求值:sin10°-根号3乘cos10°/cos40°

题目

求值:sin10°-根号3乘cos10°/cos40°

答案

答：
(sin10°-√3cos10°)/cos40°
=2*[(1/2)sin10°-(√3/2)cos10°]/cos40°
=2*[cos60°sin10°-sin60°cos10°)/cos40°
=2sin(10°-60°)/cos40°
=-2sin50°/sin50°
=-2