Sin(a-п)*cos(3п/2+a)-ctg(a-п)*sin(п/2+a)*cos(п/2-a)

Question

Sin(a-п)*cos(3п/2+a)-ctg(a-п)*sin(п/2+a)*cos(п/2-a)

Answer 1

-sin(π-α)*sinα+ctg(π-α)*cosα*sinα=-sin²α-ctgα*cosα*sinα=-sin²α-cos²α=
=-(sin²α+cos²α)=-1