theorem
  for n being Nat holds Fdfl(A,n) /\ Fdfl(B,n) = Finf((A /\ B )`,n)`
proof
  let n be Nat;
  Fdfl(A,n) /\ Fdfl(B,n) = Fdfl(A /\ B,n) by Th42
    .= Finf((A /\ B)`,n)` by Th45;
  hence thesis;
end;
