解：cos²(α-π/4)-sin²(π/4-α)=cos²(π/4-α)-sin²(π/4-α)=cos2(π/4-α)=cos(π/2-2α)=sin2α
答：cos²(a-π/4)-sin²(π/4-a)=cos²(a-π/4)-sin²(a-π/4)=cos(2a-π/2)=cos(π/2-2a)=sin2a
