set A = KurExSet ;
reconsider B = {1}, C = ((RAT (2,4)) \/ ].4,5.[) \/ ].5,+infty.[ as Subset of R^1 by TOPMETR:17;
KurExSet = {1} \/ (((RAT (2,4)) \/ ].4,5.[) \/ ].5,+infty.[) by XBOOLE_1:113;
then A1: Cl KurExSet = (Cl B) \/ (Cl C) by PRE_TOPC:20;
Cl B = {1} by BORSUK_5:38;
hence Cl KurExSet = {1} \/ [.2,+infty.[ by A1, BORSUK_5:56; :: thesis: verum