已知了x+y和x-y则x=(3-cos4a+4sin2a)/2=(3-2cos²2a+1+4sin2a)=(4-2+2sin²2a+4sin2a)/2=sin²2a+2sin2a+1=(sin2a+1)²y=(3-cos4a-4sin2a)/2=(3-2cos²2a+1-4sin2a)=(4-2+2sin²2a-4sin2a)/...