求值:(tan10°-√3)sin40°

来源:学生作业帮助网 编辑:作业帮 时间:2018/12/11 09:00:27
求值:(tan10°-√3)sin40°求值:(tan10°-√3)sin40°求值:(tan10°-√3)sin40°(tan10°-√3)sin40°=(tan10°-tan60°)sin40°=

求值:(tan10°-√3)sin40°
求值:(tan10°-√3)sin40°

求值:(tan10°-√3)sin40°
(tan10°-√3)sin40°
=(tan10°-tan60°)sin40°
=(sin10°/cos10°-sin60°/cos60°)sin40°
=sin40°*(sin10°*cos60-cos10°*sin60°)/(cos10°*cos60°)
=sin40°*sin(10°-60°)/(cos10°*1/2)
=-2sin40°*sin50°/cos10°
=[cos(40°+50°)-cos(40°-50°)]/cos10°
=(cos90°-cos10°)/cos10°
=(0-cos10°)/cos10°
=-1