(************************************************************************)
(*         *   The Coq Proof Assistant / The Coq Development Team       *)
(*  v      *   INRIA, CNRS and contributors - Copyright 1999-2018       *)
(* <O___,, *       (see CREDITS file for the list of authors)           *)
(*   \VV/  **************************************************************)
(*    //   *    This file is distributed under the terms of the         *)
(*         *     GNU Lesser General Public License Version 2.1          *)
(*         *     (see LICENSE file for the text of the license)         *)
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Local Open Scope R_scope.

(* Chasles' relation *)
Lemma tech2 :
forall (An:nat -> R) (m n:nat),
(m < n)%nat ->
sum_f_R0 An n =
sum_f_R0 An m + sum_f_R0 (fun i:nat => An (S m + i)%nat) (n - S m).