2tan(π/4-α)*sin(π/4+α)= 2sin(π/4-α)*sin(π/4+α)/[cos(π/4 - α)]而2sin(π/4-α)*sin(π/4+α)= 2cos[(π/2) - (π/4-α)]·cos[(π/2) - (π/4+α)]= 2cos[(π/4)+α]·cos[(π/4)-α]∴原式 = (2cosα ...