试用分析法证明:(1+1/sin^2θ)(1+1/cos^2θ)≥9
试用分析法证明不等式:(1+1/sin^a)(1+1/cos^a)>=9
证明下列恒等式(sinθ+cosθ)/(1-tan^2θ)+sin^2θ/(sinθ-cosθ)=sinθ+cosθ
证明1-2cos^2θ/tanθ-cotθ=sinθcosθ
证明恒等式2cos^2θ+sin^4θ=cos^4θ+1
证明下列恒等式tan^2 θ *(1-sinθ)/(1+cosθ)=(1-cosθ)/(1+sinθ)
证明下列恒等式: (1)2sin(2/π+x)cos(2/π-x)*cosθ+(2cos^2x-1)*sinθ=sin(
化简:1+sinθ+cosθ+2sinθcosθ /1+sinθ+cosθ
证明Cos^A-Sin^A=1-2Sin^A=2Cos^A-1=cos^a-sin^a
证明:1+sinα−cosα1+sinα+cosα=tanα2
证明:2(cosα−sinα)1+sinα+cosα=cosα1+sinα−sinα1+cosα
证明(sinα+cosα-1)(sinα-cosα+1)分之2sinαcosα=sinα分之1+cosα
若sin^4a/sin^2b+cos^4a/cos^2b=1,证明sin^4b/sin^2a+cos^4b/cos^2a