reserve T for TopSpace,
  A, B for Subset of T;

theorem Th1:
  Int Cl Int A /\ Int Cl Int B = Int Cl Int (A /\ B)
proof
  set C = Int A, D = Int B;
  Int Cl C /\ Int Cl D = Int Cl(C /\ D) by TDLAT_1:7;
  hence thesis by TOPS_1:17;
end;
