reserve a,x,y for object, A,B for set,
  l,m,n for Nat;
reserve X,Y for set, x for object,
  p,q for Function-yielding FinSequence,
  f,g,h for Function;
reserve m,n,k for Nat, R for Relation;

theorem
  rng R misses dom R implies iter(R,2) = {}
proof
  assume
A1: rng R misses dom R;
  thus iter(R,2) = iter(R,1+1)
    .= iter(R,1)*R by Th70
    .= R*R by Th69
    .= {} by A1,RELAT_1:44;
end;
