theorem Th48:
  for A being Cell of k,G, C being Chain of (k + 1),G holds
  A in del C iff k + 1 <= d & card(star A /\ C) is odd
proof
  let A be Cell of k,G, C be Chain of (k + 1),G;
  defpred P[Cell of k,G] means k + 1 <= d & card(star $1 /\ C) is odd;
A1: del C = { A9 where A9 is Cell of k,G : P[A9] };
  thus A in del C iff P[A] from LMOD_7:sch 7(A1);
end;
