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

theorem Ble1:
  X <> {} & Y = {} implies (CMap kappa_1 R).(X,Y) = 1
  proof
    assume
A1: X <> {} & Y = {}; then
    (CMap kappa_1 R).(X,Y) = card (X \ Y) / card (X \/ Y) by PropEx3
      .= 1 by A1,XCMPLX_1:60;
    hence thesis;
  end;
