Canonical Structure FT_c2 := Build_Com_arrow FT_eq2.
(* Diagramme 2 commute *)

(* Specifications: *)
Lemma FT_diag2 : FT_Apeps FT_i0 =_S (FT_Apeps FT_m0 o FT_t'') o FT_p.
(* Diagramme 3 commute *)
Lemma FT_diag3 : FT_Apeps FT_j0 =_S (FT_Apeps FT_m0 o FT_t'') o FT_q.
(* le grand diagramme commute : FT_eps(i) o FT_t = FT_eps(j) o FT_t' o h#' *)
Lemma FT_diag4 : FT_Apeps FT_i0 o FT_t =_S FT_Apeps FT_j0 o FT_t' o FT_h'.
(* qq i. t' o (pes i) est fleche de FT_j0 -> i dans (x|G)I *)
Lemma FT_eq3 :
forall i : FT_I,
Com_law (axf:=Build_Com_ob (FT_f FT_j0)) (bxg:=Build_Com_ob (FT_f i))
(FT_t' o FT_Apeps i).