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(*         *   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.
Definition C (n p:nat) : R :=
INR (fact n) / (INR (fact p) * INR (fact (n - p))).

Lemma pascal_step3 :
forall n i:nat, (i < n)%nat -> C n (S i) = INR (n - i) / INR (S i) * C n i.