reserve E, x, y, X for set;
reserve A, B, C for Subset of E^omega;
reserve a, a1, a2, b for Element of E^omega;
reserve i, k, l, m, n for Nat;

theorem
  A+ = A |^ (1, n) \/ A |^.. (n + 1)
proof
A1: 0 + 1 <= n + 1 by XREAL_1:7;
  thus A+ = A |^.. 1 by Th50
    .= A |^ (1, n) \/ A |^.. (n + 1) by A1,Th7;
end;
