首先有1-2sin²x=cos2x2cos²x-1=cos2xcosxcosy=1/2cos(x+y)cos(x-y)sin⁶x=1/8(1-cos2x)³(1-cos2x)³=1-3cos2x+3cos²2x-cos³2x=1-3cos2x+3/2(cos4x+1)-1/2(cos4x+1)cos2x=5/2-7/2c...