set A = KurExSet ;
Cl (Int KurExSet) = Cl ((Cl (KurExSet `)) `) by TOPS_1:def 1;
then A1: Int (Cl (Int KurExSet)) = (Cl ((Cl ((Cl (KurExSet `)) `)) `)) ` by TOPS_1:def 1;
(Cl ((Cl (KurExSet `)) `)) ` = ].-infty,4.[ by Th19, TOPMETR:17, XXREAL_1:224, XXREAL_1:294;
then Cl ((Cl ((Cl (KurExSet `)) `)) `) = ].-infty,4.] by BORSUK_5:51;
hence Int (Cl (Int KurExSet)) = ].4,+infty.[ by A1, TOPMETR:17, XXREAL_1:224, XXREAL_1:288; :: thesis: verum