reconsider B = {1}, C = ((RAT 2,4) \/ ].4,5.[) \/ ].5,+infty .[ as Subset of R^1 by TOPMETR:24;
set A = KurExSet ;
KurExSet = {1} \/ (((RAT 2,4) \/ ].4,5.[) \/ ].5,+infty .[) by XBOOLE_1:113;
then A1: Cl KurExSet = (Cl B) \/ (Cl C) by PRE_TOPC:50;
Cl B = {1} by BORSUK_5:61;
hence Cl KurExSet = {1} \/ [.2,+infty .[ by A1, BORSUK_5:82; :: thesis: verum