set A = KurExSet ;
1 in {1} by TARSKI:def 1;
then 1 in {1} \/ (RAT (2,4)) by XBOOLE_0:def 3;
then 1 in ({1} \/ (RAT (2,4))) \/ ].4,5.[ by XBOOLE_0:def 3;
then A1: 1 in KurExSet by XBOOLE_0:def 3;
Int KurExSet = ].4,5.[ \/ ].5,+infty.[ by Th18, TOPS_1:def 1;
hence KurExSet <> Int KurExSet by A1, XXREAL_1:223; :: thesis: verum