End ext_cont.
Section ext_cont'.
Context {V : NormedModule R_AbsRing}.

(* Specifications: *)
Lemma extension_cont_is_derive (f g : R -> V) (a : R) (l : V) :
is_derive f a l -> is_derive g a l
-> f a = g a
-> is_derive (extension_cont f g a) a l.