已知α ∈(π/2,π),sin α =3 / 5 则cosα =√(1-sin²α )=-4/5所以tanα=sinα/cosα=(3/5)/(-4/5)=-3/4故tan(α+π/4)=[tanα+tan(π/4)]/[1-tanα*tam(π/4)]=(-3/4+1)/(1+3/4)=1/7tan(2α+π/4)=[tan(α+...