
theorem Th2:
  for T being non empty TopSpace, V being Subset of T_0-reflex(T)
  holds V is open iff union V in the topology of T
proof
  let T be non empty TopSpace;
  let V be Subset of T_0-reflex(T);
A1: V is Subset of Indiscernible(T) by BORSUK_1:def 7;
  thus V is open implies union V in the topology of T
            by A1,BORSUK_1:27;
  assume union V in the topology of T;
  then V in the topology of space Indiscernible(T) by A1,BORSUK_1:27;
  hence thesis;
end;
