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+) \/ (B+) c= (A \/ B)+
proof
A1: A+ = A |^.. 1 by Th50;
A2: B+ = B |^.. 1 by Th50;
  (A \/ B)+ = (A \/ B) |^.. 1 by Th50;
  hence thesis by A1,A2,Th45;
end;
