fact: Definition cancelR_isequiv {A B C} (f : A -> B) {g : B -> C} `{IsEquiv A B f} `{IsEquiv A C (g o f)} : IsEquiv g := isequiv_homotopic ((g o f) o f^-1) (fun b => ap g (eisretr f b)).
imports: Basics.Overture Basics.PathGroupoids Basics.Contractible Basics.Tactics