public static double DistanceBetween(RectangularCoordinate r1, RectangularCoordinate r2)
        {
            double r = Math.Pow(r1.X - r2.X, 2) + Math.Pow(r1.Y - r2.Y, 2) + Math.Pow(r1.Z - r2.Z, 2);

            return(Math.Sqrt(r));
        }
 public double DistanceTo(RectangularCoordinate r) => DistanceBetween(this, r);
 public RectangularCoordinate(RectangularCoordinate r) : this(r.X, r.Y, r.Z)
 {
 }