reserve T for 1-sorted;
reserve T for TopSpace;

theorem Th25:
  for A being Subset of T st A is condensed holds Int A is open_condensed
proof
  let A be Subset of T;
  assume
A1: A is condensed;
  then A c= Cl Int A by TOPS_1:def 6;
  then
A2: Int A c= Int Cl Int A by TOPS_1:19;
  Int A is condensed by A1,TOPS_1:71;
  then Int Cl Int A c= Int A by TOPS_1:def 6;
  then Int Cl Int A = Int A by A2;
  hence thesis by TOPS_1:def 8;
end;
