tan2α=tan(α+β+α-β)
=tan(〔α+β﹚+tan(α-β))/(1-,tan(α-β)tan(α+β))
=(3/5+1/4)/(1-3/5x1/4)
=1
tan2α=2tanα/(1-tanα^2)=1
tanα=-1-√2或-1+√2
tan(α+π/4）=(tanα+1)/(1-tanα)
=-1-√2或1+√2