化简2cos*2-1 / 2tan(π/4-x)sin*2（π/4+x）

分母=2tan(π/4-x)*cos^2[π/2-(π/4+x)] =2[sin(π/4-x)/cos(π/4-x)]*cos^2(π/4-x) =2sin(π/4-x)cos(π/4-x) =sin[2(π/4-x)] =sin(π/2-2x) =cos2x 分子=1/2[4cos^4(x)-4cos^2(x)+1] =1/2(2cos^2x-1)^2 =1/2(co...