tanθ=1/3,cos^2θ+sinθcosθ等于

问题描述:

tanθ=1/3,cos^2θ+sinθcosθ等于

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