(* SYMMETRICALLY, OK: *)

Lemma expf_L0_5bis:forall (m:fmap)(x y z t:dart),
inv_hmap (L m zero x y) -> exd m z ->
let x_1 := cA_1 m one x in
~ expf m x_1 y ->
(expf m x_1 z /\ expf m x_1 t
\/ expf m y z /\ expf m y t)
-> expf (L m zero x y) z t.