set F = the topology of X;
let A be object ; :: according to TARSKI:def 3,CANTOR_1:def 2 :: thesis: ( not A in the topology of X or A in UniCl the topology of X )
assume A1: A in the topology of X ; :: thesis: A in UniCl the topology of X
then reconsider B = {A} as Subset-Family of X by SUBSET_1:41;
A2: B c= the topology of X by A1, ZFMISC_1:31;
A = union B by ZFMISC_1:25;
hence A in UniCl the topology of X by A2, Def1; :: thesis: verum