public void Add_SinCosLn_To_Summand(double a, double b, int index)
{
if (All_Functions.Multiplicands == null)
All_Functions.Multiplicands = new List<IElementaryFunction>();
if(index == 0)
All_Functions.Multiplicands.Add(new Sine { Aparam = a, Bparam = b });
if (index == 1)
All_Functions.Multiplicands.Add(new Cosine { Aparam = a, Bparam = b });
if (index == 2)
All_Functions.Multiplicands.Add(new LogarithmicFunction { Aparam = a, Bparam = b });
}