3sinβ=sin(2α+β)----》3tan(β)=sin(2α)+cos(2α)tan(β).(1)
tanα=1----->sina=cosa,sina^2=cosa^2=1/2
sin2a=2*1/2=1,cos2a=0
由（1）式得tanβ=1/3
所以tan2β=3/4
α=nπ+π、4,2α=2nπ+π/2
所以原式=-tan2β=-3/4