(* Specializations: *)

(* Specifications: *)
Lemma exd_cA:forall (m:fmap)(k:dim)(z:dart),
inv_hmap m ->
(exd m z <-> exd m (cA m k z)).
Lemma exd_cA_1:forall (m:fmap)(k:dim)(z:dart),
inv_hmap m ->
(exd m z <-> exd m (cA_1 m k z)).