reserve P for Element of BK_model;
reserve N,N1,N2 for invertible Matrix of 3,F_Real;
reserve l,l1,l2 for Element of the Lines of IncProjSp_of real_projective_plane;

theorem Th18:
  1_GroupLineHomography3 = line_homography(1.(F_Real,3))
  proof
    for h being Element of GLH3 holds h * e = h & e * h = h by Lm1;
    hence thesis by GROUP_1:4;
  end;
