sin2(x-π/4)=sin(2x-π/2)=-cos2x=-(1-2(sina)^2)=2(sina)^2-1因为sinx=(√5-1)/2,所以sin2(x-π/4)=2((√5-1)/2)^2-1=2-√5sin(2x-π/2)=-cos2x如图单位长度为半径的圆,假定OA与x轴正半轴的夹角是2x,则2x-π/2就是...