看不懂你写的东西。我给你解一下原题吧。分子=cos2α分母=2tan[π/2-(π/4+α)]sin^2(π/4+α)=2cot(π/4+α)sin^2(π/4+α)=2cos(π/4+α)sin(π/4+α)=sin[2(π/4+α)]=sin(π/2+2α)=cos2α于是原式=cos2α/cos2α=1
