reserve a,b,c,d,e,f for Real,
        g           for positive Real,
        x,y         for Complex,
        S,T         for Element of REAL 2,
        u,v,w       for Element of TOP-REAL 3;
reserve a,b,c for Element of F_Real,
          M,N for Matrix of 3,F_Real;
reserve D        for non empty set;
reserve d1,d2,d3 for Element of D;
reserve A        for Matrix of 1,3,D;
reserve B        for Matrix of 3,1,D;
reserve u,v for non zero Element of TOP-REAL 3;
reserve P,Q,R for POINT of IncProjSp_of real_projective_plane,
            L for LINE of IncProjSp_of real_projective_plane,
        p,q,r for Point of real_projective_plane;

theorem Th60:
  ex p,q st p <> q & L = Line(p,q)
  proof
    L in the Lines of IncProjSp_of real_projective_plane;
    then L in ProjectiveLines real_projective_plane by INCPROJ:2;
    then L in {B where B is Subset of real_projective_plane:
                B is LINE of real_projective_plane} by INCPROJ:def 1;
    then ex B be Subset of real_projective_plane st L = B &
      B is LINE of real_projective_plane;
    hence thesis by COLLSP:def 7;
  end;
