End Div_Mod.
Section Same_sign.

(* Specifications: *)
Theorem Zsame_sign_trans :
forall v u w, v <> Z0 ->
(0 <= u * v)%Z -> (0 <= v * w)%Z -> (0 <= u * w)%Z.
Theorem Zsame_sign_trans_weak :
forall v u w, (v = Z0 -> w = Z0) ->
(0 <= u * v)%Z -> (0 <= v * w)%Z -> (0 <= u * w)%Z.
Theorem Zsame_sign_imp :
forall u v,
(0 < u -> 0 <= v)%Z ->
(0 < -u -> 0 <= -v)%Z ->
(0 <= u * v)%Z.
Theorem Zsame_sign_odiv :
forall u v, (0 <= v)%Z ->
(0 <= u * Z.quot u v)%Z.