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).

Lemma norm_triangle_inv :
forall x y : V,
Rabs (norm x - norm y) <= norm (minus x y).