tan((α+β)-(α-π/4))=tan(β+π/4)=(
tan(α+β)-tan(α-π/4))/ 1+ tan(α+β)*tan(α-π/4)
=1
tan((α+β)-(α-π/4))=tan(β+π/4)=(
tan(α+β)-tan(α-π/4))/ 1+ tan(α+β)*tan(α-π/4)
=1