Definition Ker : submodule Mod.Definition coKer : submodule Mod2.

(* Specifications: *)
Lemma Ker_prop : forall x : Mod, in_part x Ker -> Equal (f x) (monoid_unit Mod2).
Lemma Ker_prop_rev : forall x : Mod, Equal (f x) (monoid_unit Mod2) -> in_part x Ker.
Lemma coKer_prop : forall x : Mod, in_part (f x) coKer.