Lemma cF_L1_x10:forall(m:fmap)(x y:dart), inv_hmap m -> prec_L m one x y -> let m1:= L m one x y in let y0 := cA m zero y in let y_1 := cA_1 m one y in let dx := MF.degree m x in ~expf m x y0 -> Iter (cF m1) dx x = y_1.