利用诱导公式:sin(π/4+α)=cos(π/4-α)∴ 2cos²α-1/【2sin(π/4-α)sin²(π/4+α)】=2cos²α-1/【2sin(π/4-α)cos²(π/4-α)】=cos2α/[sin(π/4-α)*sin(π/2-2α)]=cos2α/[sin(π/4-α)*...