第1个回答 2012-04-22
解:
sin40°(tan10°-√3)
=sin40°*2*(1/2*sin10°-√3/2*cos10°)/cos30°
=2sin40°(cos60°sin10°-sin60°cos10°)/cos10°
=2sin40°[sin10°cos60°-cos10°sin60°]/cos10°
=2sin40*sin(-50°)/cos10°
=-2sin40*sin50°/cos10°
=-2sin40°cos40°/cos10°
=-sin80°/cos10°
=-cos10°/cos10°
=-1