cos20°-cos40°+cos60°+cos100°的值等于 ______.
题型:不详难度:来源:
cos20°-cos40°+cos60°+cos100°的值等于 ______. |
答案
cos20°-cos40°+cos60°+cos100° =cos(60°-40°)+cos(60°+40°)-cos40°+cos60° =2cos60°cos40°-cos40°+cos60° =cos60° = 故答案为: |
举一反三
已知cosα=,cos(α+β)=-,α、β∈(0,),求β. |
cos24°sin54°-cos66°sin36°的值为( ) |
sinα=,cosβ=,其中α、β∈(0,),则α+β=______. |
已知向量a=(sin55°,sin35°),b=(sin25°,sin65°),则•=______. |
最新试题
热门考点