题目

证明1-2cos^2θ/tanθ-cotθ=sinθcosθ

提问时间：2020-10-03

答案

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