如果(1-tanx)/(1+tanx)=4+√5 则tan(π/4+x)=?
问题描述：
如果(1-tanx)/(1+tanx)=4+√5 则tan(π/4+x)=?
答
tan(π/4+x)=sin(x+π/4)/cos(x+π/4)=sin(x+π/4)/sin(π/4-x)=sin(x+π/4)/(-sin(x-π/4))=(sinx+cosx)/(cosx-sinx)=(tanx+1)/(1-tanx)=1/(4+√5)=(4-√5)/11