如果等式成立：式左=tan(2α/2)+1/tan(π/4+α/2)=2tan(α/2)/(1-(tan(α/2)^2)+(1-tan(π/4)tan(α/2))/(tan(π/4)+tan(α/2))=(1+(tan(α/2))^2)/(1-(tan(α/2))^2)=1/((cos(α/2))^2-(sin(α/2))^2)=1/cosα式右=...