Definition islinv' {X : hSet} (x1 : X) (op : binop X) (exinv : hsubtype X) (inv : carrier_subset exinv -> X) := ∏ (x : X) (Hx : exinv x), op (inv (x ,, Hx)) x = x1.
Require Import UniMath.MoreFoundations.Tactics. Require Import UniMath.MoreFoundations.Sets. Require Import UniMath.MoreFoundations.Orders. Require Import UniMath.Algebra.BinaryOperations