It is known that both α and β are acute angles, and COS (α + β) = sin (α - β), then Tan α=______ .

It is known that both α and β are acute angles, and COS (α + β) = sin (α - β), then Tan α=______ .

∵ cos (α + β) = sin (α - β), ∵ cos α cos β - sin α sin β = sin α cos β - cos α sin β, that is, cos β (sin α - cos α) + sin β (sin α - cos α) = 0, ∵ α, β are acute angles, ∵ cos β + sin β > 0, ∵ sin α - cos α = 0, ∵ Tan α = 1