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

(* 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).