tan(π/4-x)=cot[π/2-(π/4-x)]=cot(π/4+x)=1/tan(π/4+x)所以tan(π/4+x)=3/tan(π/4+x)tan²(π/4+x)=3tan(π/4+x)=±√3tanπ/4=1所以tan(π/4+x)=(1+tanx)/(1-tanx)=±√3tanx=2-√3,tanx=2+√3