证明：左边=[tan(x/2) +tan(π/4)]/[1 - tan(x/2)tan(π/4)] + [tan(x/2) - tan(π/4)]/[1 + tan(x/2)tan(π/4)]=[tan(x/2) +1 ]/[1 - tan(x/2)] + [tan(x/2) - 1]/[1 + tan(x/2)](对该式通分后得到下式)={[ta...