}// getCoordinates
/// <summary>
/// scalar product between this and w.
/// </summary>
/// <param name="w">the second factor; the first factor is "this"</param>
/// <returns></returns>
public double scalarProduct(PointR2 w)
{
PointR3 v_inR3 = new PointR3(this.x, this.y, 0);
PointR3 w_inR3 = new PointR3(w.x, w.y, 0);
double scalar_inR3 = v_inR3.scalarProduct(w_inR3);
// ready.
return(scalar_inR3);
}// end scalarProduct
