tan(θ+π/4)=[tanθ+tan(π/4)]/[1-tanθtan(π/4)]=(tanθ+1)/(1-tanθ)=2即tanθ+1=2(1-tanθ)解得：tanθ=1/3 tan(2θ+π/4)=tan[θ+(θ+π/4)]=[tanθ+tan(θ+π/4)]/[1-tanθtan(θ+π/4)]=(1/3+2)/[1-(1/3)*2...