 reserve R for finite Approximation_Space;
 reserve X,Y,Z for Subset of R;
 reserve kap for RIF of R;

theorem :: Proposition 6 f)
  (X = {} & Y <> {}) or (X <> {} & Y = {}) implies
    (CMap kappa R).(X,Y) + (CMap kappa R).(Y,X) =
      (CMap kappa_1 R).(X,Y) + (CMap kappa_1 R).(Y,X) = 1
  proof
    assume
A1: (X = {} & Y <> {}) or (X <> {} & Y = {}); then
    (CMap kappa R).(X,Y) + (CMap kappa R).(Y,X) = 1 by Lemma6f;
    hence thesis by A1,Lemma6f1;
  end;
