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

theorem
  <%>E in B implies A c= A ^^ (B |^ l) & A c= (B |^ l) ^^ A
proof
  assume <%>E in B;
  then <%>E in B |^ l by FLANG_1:30;
  hence thesis by FLANG_1:16;
end;
