Выражение sin(a-b)-sin(п/2-a)*sin(-b)

= sin(a)*cos(b) - cos(a)*sin(b) + cos(a)*sin(b) = sin(a) * cos(b)

Sin(α-β)-sin(π/2-α)·sin(-β)=sin(α-β)+cosα·sinβ=
=sinα·cosβ-cosa·sinβ+cosα·sinβ=sinα·cosβ