(* Lemma RInt_comp_opp (f : R -> V) (a b : R) : ex_RInt f (-a) (-b) -> RInt (fun y => f (- y)) a b = opp (RInt f (-a) (-b)). *)

Lemma RInt_comp_lin (f : R -> V) (u v a b : R) :
ex_RInt f (u * a + v) (u * b + v) ->
RInt (fun y => scal u (f (u * y + v))) a b = RInt f (u * a + v) (u * b + v).