(************************************************************************)
(*         *      The Rocq Prover / The Rocq Development Team           *)
(*  v      *         Copyright INRIA, CNRS and contributors             *)
(* <O___,, * (see version control and CREDITS file for authors & dates) *)
(*   \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).