Lemma other_faces_in_cut_B0:forall (m:fmap)(x z t:dart), inv_hmap m -> succ m zero x -> let y := A m zero x in let x0 := bottom m zero x in ~expf m y x0 -> ~expf m y z -> ~expf m x0 z -> (expf m z t <-> expf (B m zero x) z t).