theorem 
  not (a = 0 & b = 0 & c = 0 & d = 0 & e = 0 & f = 0) &
  {P1,P2,P3,P4,P5,P6} c= conic(a,b,c,d,e,f) &
  P1,P2,P3,P4,P5,P6,P7,P8,P9 are_in_Pascal_configuration
  implies
  P7,P8,P9 are_collinear
  proof
    per cases;
    suppose P1,P2,P3 are_collinear;
      hence thesis by Th35;
    end;
    suppose not P1,P2,P3 are_collinear;
      hence thesis by Th34;
    end;
  end;
