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