求值(1-2sinθcosθ)/(cos^2θ-sin^2θ)-(1-tanθ)/(1+tanθ)=?

sin^2θ/sinθ-cosθ + cosθ/1-tanθ = sin^2θ/sinθ-cosθ + cosθ/1-( 证明下列恒等式(sinθ+cosθ)/(1-tan^2θ)+sin^2θ/(sinθ-cosθ)=sinθ+cosθ 已知tanθ=2,求值sin^2θ+sinθcosθ-2cos^2θ 已知tanθ=根号2,求(1)(cosθ+sinθ)/(cosθ-sinθ)；（2）sin²θ-sinθcos 证明1-2cos^2θ/tanθ-cotθ=sinθcosθ 已知tan(θ+π/4)=-2,求cosθ平方+sinθcosθ-1 tanθ=2,sinθ平方+2sinθcosθ+1的值 求证 (sinθ+cosθ-1)(sinθ-cosθ+1)) /sin2θ=tanθ/2 求证(sinθ+cosθ-1)(sinθ-cosθ+1)/sin2θ=tanθ/2 证明下列恒等式tan^2 θ *(1-sinθ)/(1+cosθ)=(1-cosθ)/(1+sinθ) tanθ /2=2/3求1—cosθ +sinθ /1+cosθ +sinθ 已知tanθ/2=3,求1-cosθ+sinθ/1+cosθ+sinθ值