cos(α-β)=1/3,cosβ=3/4,α-β∈(0,π/2),β∈(0,π/2),
sin(α-β)=2√2/3,sinβ=√7/4
sinα=sin[(α-β)+β]=sin(α-β)cosβ+cos(α-β)sinβ
=2√2/3*3/4+1/3*√7/4
=(2√2+√7)/12