sin(α+β)=sinαcosβ+cosαsinβ=1/2.
∵sinαcosβ=3/4.
cosαsinβ=1/2-sinαcosβ.
=1/2-3/4.
=-1/4.
sin(α-β)=sinαcosβ-cosαsinβ.
=3/4-(-1/4).
=1.