/// <summary>
/// Calculates sum.
/// </summary>
/// <param name="addend">Addend value.</param>
/// <returns>Sum.</returns>
public Vector Sum(double addend)
{
Vector result = this;
result.I = result.SumInI(addend);
result.J = result.SumInJ(addend);
result.K = result.SumInK(addend);
return(result);
}