docs: public double[][] lines_of_polygon(double[][] p) {
      double[][] c9 = new double[p.length][3];
      for (int i = 0; i < p.length - 1; i++) {//		evaluate formula of the straight line l1,...,m-1
        c9[i] = line_of_twoP(p[i], p[i + 1]);
      }
      // evaluate formula of the straight line lm
      c9[p.length - 1] = line_of_twoP(p[p.length - 1], p[0]);
      return c9;
    }