Lemma isrigfuninvmap {X Y : rig} (f : rigiso X Y) : isrigfun (invmap f). Proof. intros. split. - apply (ismonoidfuninvmap (rigaddiso f)). - apply (ismonoidfuninvmap (rigmultiso f)). Defined.
Require Import UniMath.Algebra.Groups. Require Import UniMath.MoreFoundations.Sets. Require Import UniMath.MoreFoundations.Orders.