tanθ=1/3,cos^2θ+sinθcosθ等于
问题描述:
tanθ=1/3,cos^2θ+sinθcosθ等于
答
cos²θ+sinθcosθ
=(cos²θ+sinθcosθ)/1
=(cos²θ+sinθcosθ)/(sin²θ+cos²θ)
=(1+tanθ)/(tan²θ+1)
=(1+1/3)/[(1/9)+1]
=6/5
关键是“1”的代换