Section Properties3.
Context {K : AbsRing} {V : NormedModule K}.
exact is_series_scal.
Qed.
exact ex_series_scal.
Qed.
End Properties3.
(** * D'Alembert criterion *)
(** * Geometric series *)

Lemma ex_series_geom (q : R) :
Rabs q < 1 -> ex_series  (fun n => q ^ n).