植物都有哪些相同点:(tan10°-根号3)tan40°=?要过程

来源:百度文库 编辑:查人人中国名人网 时间:2024/05/14 07:08:29

解:(tan10°-√3)tan40°
=(sin10°/cos10°-√3cos10°/cos10°)×(sin40°/cos40°)
=[(sin10°-√3cos10°)/cos10°]×(sin40°/cos40°)
=2[(sin30°sin10°-cos30°cos10°)/cos10°]×(sin40°/cos40°)
=-2(cos40°/cos10°)×(sin40°/cos40°)
=-2sin40°/cos10°
=-2sin40°/sin80°
=-2sin40°/(2sin40°cos40°)
=-1/cos40°
=-sec40°