(** ** Chasles *)

(* Specifications: *)
Lemma is_RInt_Chasles_0 (f : R -> V) (a b c : R) (l1 l2 : V) :
a < b < c -> is_RInt f a b l1 -> is_RInt f b c l2
-> is_RInt f a c (plus l1 l2).
Lemma ex_RInt_Chasles_0 (f : R -> V) (a b c : R) :
a <= b <= c -> ex_RInt f a b -> ex_RInt f b c
-> ex_RInt f a c.
Lemma is_RInt_Chasles_1 (f : R -> V) (a b c : R) l1 l2 :
a < b < c -> is_RInt f a c l1 -> is_RInt f b c l2 -> is_RInt f a b (minus l1 l2).
Lemma is_RInt_Chasles_2 (f : R -> V) (a b c : R) l1 l2 :
a < b < c -> is_RInt f a c l1 -> is_RInt f a b l2 -> is_RInt f b c (minus l1 l2).
Lemma is_RInt_Chasles (f : R -> V) (a b c : R) (l1 l2 : V) :
is_RInt f a b l1 -> is_RInt f b c l2
-> is_RInt f a c (plus l1 l2).
Lemma ex_RInt_Chasles (f : R -> V) (a b c : R) :
ex_RInt f a b -> ex_RInt f b c -> ex_RInt f a c.