(2(cosx)^4-2(cosx)^2+1/2)/2tan(45-x)[sin(45+x)]^2
=1/2(4(cosx)^4-4(cosx)^2+1)/2tan(45°-x)cos²(45°-x)
=1/2（2cos²x-1）²/2sin（45°-x）cos（45°-x）=1/2cos²2x/sin（90°-2x）=1/2cos²2x/cos2x
=1/2cos2x