(** ** Additive operators *)
(** Opposite of functions *)
Section Opp.
Context {K : AbsRing} {V : NormedModule K}.

(* Specifications: *)
Lemma is_derive_opp :
forall (f : K -> V) (x : K) (l : V),
is_derive f x l ->
is_derive (fun x => opp (f x)) x (opp l).
Lemma ex_derive_opp :
forall (f : K -> V) (x : K),
ex_derive f x ->
ex_derive (fun x => opp (f x)) x.