Section NormedModule1.
Context {K : AbsRing} {V : NormedModule K}.
Definition norm : V -> R := NormedModule.norm K _ (NormedModule.class K V).
Definition norm_factor : R := NormedModule.norm_factor K _ (NormedModule.class K V).
Definition ball_norm (x : V) (eps : R) (y : V) := norm (minus y x) < eps.
Definition locally_norm (x : V) (P : V -> Prop) :=
exists eps : posreal, forall y, ball_norm x eps y -> P y.

Lemma ball_norm_sym :
forall (x y : V) (eps : posreal), ball_norm x eps y -> ball_norm y eps x.