code: public static int dot (int vsx, int vsy, int v1ex, int v1ey, int v2ex, int v2ey)
      {
          return ((v1ex - vsx) * (v2ex - vsx) + (v1ey - vsy) * (v2ey - vsy));
      }
docs: Computes and returns the dot product of the two vectors.  See {@link
  #dot(Point,Point,Point)} for an explanation of the arguments