(** * Definitions on [R] *)

Definition Derive (f : R -> R) (x : R) := real (Lim (fun h => (f (x+h) - f x)/h) 0).

Lemma ex_derive_scal_l : forall (f : K -> K) (x : K) (k : V), ex_derive f x -> ex_derive (fun x => scal (f x) k) x.