theorem
  union(Cl Int Cl F) c= Cl Int Cl(union F)
proof
A1: Cl(union Int Cl F) c= Cl Int Cl(union F) by Th50,PRE_TOPC:19;
  union(Cl Int Cl F) c= Cl(union Int Cl F) by Th15;
  hence thesis by A1;
end;
