
theorem
  for A being Preorder holds
    the InternalRel of A quasi_orders the carrier of A
proof
  let A be Preorder;
  the InternalRel of A is_reflexive_in the carrier of A &
    the InternalRel of A is_transitive_in the carrier of A
    by ORDERS_2:def 2, ORDERS_2:def 3;
  hence thesis by ORDERS_1:def 7;
end;
