code: public static final double getAngleBetweenTwoLines(final Point2D p0, final Point2D p1, final Point2D p2)
      {
          return getAngleFromSSS(p0.distance(p1), p1.distance(p2), p0.distance(p2));
      }
docs: Returns the angle between p2 -> p0 and p2 -> p2