证明1-2cos^2θ/tanθ-cotθ=sinθcosθ
问题描述：
证明1-2cos^2θ/tanθ-cotθ=sinθcosθ
答
左边=(1-cos^2(θ))/(sinθ/cosθ-cosθ/sinθ)=(sin^2(θ)-cos^2(θ))/((sin^2(θ)-cos^2(θ)/(sinθcosθ))=1/(1/(sinθcosθ))=sinθcosθ