(* COROLLARY: *)

Lemma expf_impl_expf_L1:forall(m:fmap)(x y z t:dart),
let m1:= L m one x y in
let y0:= cA m zero y in
inv_hmap m1 -> ~expf m x y0
-> ~expf m x z -> ~expf m y0 t ->
expf m z t -> expf m1 z t.