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

theorem Th1:
  A misses B implies Int A misses Int B
  proof
    assume
A1: A misses B;
    Int A c= A & Int B c= B by TOPS_1:16;
    then Int A /\ Int B c= {} by A1,XBOOLE_1:27;
    hence thesis;
  end;
