red.
intro.
apply H.
apply divides_antisym;trivial.
apply one_min_div.
Qed.

(* Specifications: *)
(** if d | a and d | b then d | (a+b) *)
Lemma divides_plus : forall (d a b:nat),(divides a d)->(divides b d)->(divides (plus a b) d).
unfold divides.