Definition expfo(m:fmap)(x:dart)(z t:dart):=
expf (L (B m zero x) zero x (A m zero x)) z t.

(* Specifications: *)
Lemma expfo_expf:forall(m:fmap)(x:dart)(z t:dart),
inv_hmap m -> succ m zero x ->
(expfo m x z t <-> expf m z t).