sqrt(2) * cos（2x-π/4）= cos(2x) + sin(2x)
sin(x + pi/2) = -cos(x)
1 + cos(2x) = 2 * cos^2(x)
sin(2x) = 2 * sin(x) * cos(x)
所以最终结果为 -2 * cos(x) - 2 * sin(x)