1) Sin(x +y) - CosxSiny = SinxCos + CosxSiny -CosxSiny = SinxCosy
2)Cos(x -y) -SinxSiny = CosxCosy + SinxSiny -SinxSiny = CosxCosy
3)SinαCosβ - Sin(α - β) =SinαCosβ - SinαCosβ + CosαSinβ = CosαSinβ
4) CosαCosβ - Cos(α -β) = CosαCosβ - CosαCosβ -SinαSinβ =
=-SinαSinβ