(* THEN, THE RESULT: *)

Theorem degree_L1_split: forall(m:fmap)(x y:dart),
let m1:= L m one x y in
let y0 := cA m zero y in
let y_1:= cA_1 m one y in
inv_hmap (L m one x y) ->
expf m x y0 ->
MF.degree m x = MF.degree m1 x + MF.degree m1 y_1.