【cos2x=cos²x-sin²xsin2x=2sinxcosxsinx+cosx=√2sin(x+π/4) 】f（x）=1-2sin^2 （x+派/8）+2sin（x+派/8）cos（x+派/8）=sin²(x+π/8)+cos²(x+π/8)-2sin²(x+π/8)+2sin(x+π/8)cos(x+...