reserve P,Q,X,Y,Z for set, p,x,x9,x1,x2,y,z for object;
reserve D for non empty set;

theorem
  for f being PartFunc of X,Y st dom f = X holds f is Function of X,Y
proof
  let f be PartFunc of X,Y;
  rng f c= Y;
  hence thesis by Th2;
end;
