reserve Omega for non empty set,
        Sigma for SigmaField of Omega,
        Prob for Probability of Sigma,
        A for SetSequence of Sigma,
        n,n1,n2 for Nat;

theorem Th9:
  (inferior_setsequence Complement A).n = ((superior_setsequence A).n)`
proof
  set B = Complement A;
  n in NAT by ORDINAL1:def 12; then
  (inferior_setsequence B).n = ((superior_setsequence Complement B ).n)`
    by SETLIM_1:30;
  hence thesis;
end;
