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Diffstat (limited to 'theories/Reals/Rbasic_fun.v')
| -rw-r--r-- | theories/Reals/Rbasic_fun.v | 470 |
1 files changed, 470 insertions, 0 deletions
diff --git a/theories/Reals/Rbasic_fun.v b/theories/Reals/Rbasic_fun.v new file mode 100644 index 00000000..49ba48f7 --- /dev/null +++ b/theories/Reals/Rbasic_fun.v @@ -0,0 +1,470 @@ +(************************************************************************) +(* v * The Coq Proof Assistant / The Coq Development Team *) +(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *) +(* \VV/ **************************************************************) +(* // * This file is distributed under the terms of the *) +(* * GNU Lesser General Public License Version 2.1 *) +(************************************************************************) + +(*i $Id: Rbasic_fun.v,v 1.22.2.1 2004/07/16 19:31:12 herbelin Exp $ i*) + +(*********************************************************) +(** Complements for the real numbers *) +(* *) +(*********************************************************) + +Require Import Rbase. +Require Import R_Ifp. +Require Import Fourier. Open Local Scope R_scope. + +Implicit Type r : R. + +(*******************************) +(** Rmin *) +(*******************************) + +(*********) +Definition Rmin (x y:R) : R := + match Rle_dec x y with + | left _ => x + | right _ => y + end. + +(*********) +Lemma Rmin_Rgt_l : forall r1 r2 r, Rmin r1 r2 > r -> r1 > r /\ r2 > r. +intros r1 r2 r; unfold Rmin in |- *; case (Rle_dec r1 r2); intros. +split. +assumption. +unfold Rgt in |- *; unfold Rgt in H; exact (Rlt_le_trans r r1 r2 H r0). +split. +generalize (Rnot_le_lt r1 r2 n); intro; exact (Rgt_trans r1 r2 r H0 H). +assumption. +Qed. + +(*********) +Lemma Rmin_Rgt_r : forall r1 r2 r, r1 > r /\ r2 > r -> Rmin r1 r2 > r. +intros; unfold Rmin in |- *; case (Rle_dec r1 r2); elim H; clear H; intros; + assumption. +Qed. + +(*********) +Lemma Rmin_Rgt : forall r1 r2 r, Rmin r1 r2 > r <-> r1 > r /\ r2 > r. +intros; split. +exact (Rmin_Rgt_l r1 r2 r). +exact (Rmin_Rgt_r r1 r2 r). +Qed. + +(*********) +Lemma Rmin_l : forall x y:R, Rmin x y <= x. +intros; unfold Rmin in |- *; case (Rle_dec x y); intro H1; + [ right; reflexivity | auto with real ]. +Qed. + +(*********) +Lemma Rmin_r : forall x y:R, Rmin x y <= y. +intros; unfold Rmin in |- *; case (Rle_dec x y); intro H1; + [ assumption | auto with real ]. +Qed. + +(*********) +Lemma Rmin_comm : forall a b:R, Rmin a b = Rmin b a. +intros; unfold Rmin in |- *; case (Rle_dec a b); case (Rle_dec b a); intros; + try reflexivity || (apply Rle_antisym; assumption || auto with real). +Qed. + +(*********) +Lemma Rmin_stable_in_posreal : forall x y:posreal, 0 < Rmin x y. +intros; apply Rmin_Rgt_r; split; [ apply (cond_pos x) | apply (cond_pos y) ]. +Qed. + +(*******************************) +(** Rmax *) +(*******************************) + +(*********) +Definition Rmax (x y:R) : R := + match Rle_dec x y with + | left _ => y + | right _ => x + end. + +(*********) +Lemma Rmax_Rle : forall r1 r2 r, r <= Rmax r1 r2 <-> r <= r1 \/ r <= r2. +intros; split. +unfold Rmax in |- *; case (Rle_dec r1 r2); intros; auto. +intro; unfold Rmax in |- *; case (Rle_dec r1 r2); elim H; clear H; intros; + auto. +apply (Rle_trans r r1 r2); auto. +generalize (Rnot_le_lt r1 r2 n); clear n; intro; unfold Rgt in H0; + apply (Rlt_le r r1 (Rle_lt_trans r r2 r1 H H0)). +Qed. + +Lemma RmaxLess1 : forall r1 r2, r1 <= Rmax r1 r2. +intros r1 r2; unfold Rmax in |- *; case (Rle_dec r1 r2); auto with real. +Qed. + +Lemma RmaxLess2 : forall r1 r2, r2 <= Rmax r1 r2. +intros r1 r2; unfold Rmax in |- *; case (Rle_dec r1 r2); auto with real. +Qed. + +Lemma RmaxSym : forall p q:R, Rmax p q = Rmax q p. +intros p q; unfold Rmax in |- *; case (Rle_dec p q); case (Rle_dec q p); auto; + intros H1 H2; apply Rle_antisym; auto with real. +Qed. + +Lemma RmaxRmult : + forall (p q:R) r, 0 <= r -> Rmax (r * p) (r * q) = r * Rmax p q. +intros p q r H; unfold Rmax in |- *. +case (Rle_dec p q); case (Rle_dec (r * p) (r * q)); auto; intros H1 H2; auto. +case H; intros E1. +case H1; auto with real. +rewrite <- E1; repeat rewrite Rmult_0_l; auto. +case H; intros E1. +case H2; auto with real. +apply Rmult_le_reg_l with (r := r); auto. +rewrite <- E1; repeat rewrite Rmult_0_l; auto. +Qed. + +Lemma Rmax_stable_in_negreal : forall x y:negreal, Rmax x y < 0. +intros; unfold Rmax in |- *; case (Rle_dec x y); intro; + [ apply (cond_neg y) | apply (cond_neg x) ]. +Qed. + +(*******************************) +(** Rabsolu *) +(*******************************) + +(*********) +Lemma Rcase_abs : forall r, {r < 0} + {r >= 0}. +intro; generalize (Rle_dec 0 r); intro X; elim X; intro; clear X. +right; apply (Rle_ge 0 r a). +left; fold (0 > r) in |- *; apply (Rnot_le_lt 0 r b). +Qed. + +(*********) +Definition Rabs r : R := + match Rcase_abs r with + | left _ => - r + | right _ => r + end. + +(*********) +Lemma Rabs_R0 : Rabs 0 = 0. +unfold Rabs in |- *; case (Rcase_abs 0); auto; intro. +generalize (Rlt_irrefl 0); intro; elimtype False; auto. +Qed. + +Lemma Rabs_R1 : Rabs 1 = 1. +unfold Rabs in |- *; case (Rcase_abs 1); auto with real. +intros H; absurd (1 < 0); auto with real. +Qed. + +(*********) +Lemma Rabs_no_R0 : forall r, r <> 0 -> Rabs r <> 0. +intros; unfold Rabs in |- *; case (Rcase_abs r); intro; auto. +apply Ropp_neq_0_compat; auto. +Qed. + +(*********) +Lemma Rabs_left : forall r, r < 0 -> Rabs r = - r. +intros; unfold Rabs in |- *; case (Rcase_abs r); trivial; intro; + absurd (r >= 0). +exact (Rlt_not_ge r 0 H). +assumption. +Qed. + +(*********) +Lemma Rabs_right : forall r, r >= 0 -> Rabs r = r. +intros; unfold Rabs in |- *; case (Rcase_abs r); intro. +absurd (r >= 0). +exact (Rlt_not_ge r 0 r0). +assumption. +trivial. +Qed. + +Lemma Rabs_left1 : forall a:R, a <= 0 -> Rabs a = - a. +intros a H; case H; intros H1. +apply Rabs_left; auto. +rewrite H1; simpl in |- *; rewrite Rabs_right; auto with real. +Qed. + +(*********) +Lemma Rabs_pos : forall x:R, 0 <= Rabs x. +intros; unfold Rabs in |- *; case (Rcase_abs x); intro. +generalize (Ropp_lt_gt_contravar x 0 r); intro; unfold Rgt in H; + rewrite Ropp_0 in H; unfold Rle in |- *; left; assumption. +apply Rge_le; assumption. +Qed. + +Lemma RRle_abs : forall x:R, x <= Rabs x. +intro; unfold Rabs in |- *; case (Rcase_abs x); intros; fourier. +Qed. + +(*********) +Lemma Rabs_pos_eq : forall x:R, 0 <= x -> Rabs x = x. +intros; unfold Rabs in |- *; case (Rcase_abs x); intro; + [ generalize (Rgt_not_le 0 x r); intro; elimtype False; auto | trivial ]. +Qed. + +(*********) +Lemma Rabs_Rabsolu : forall x:R, Rabs (Rabs x) = Rabs x. +intro; apply (Rabs_pos_eq (Rabs x) (Rabs_pos x)). +Qed. + +(*********) +Lemma Rabs_pos_lt : forall x:R, x <> 0 -> 0 < Rabs x. +intros; generalize (Rabs_pos x); intro; unfold Rle in H0; elim H0; intro; + auto. +elimtype False; clear H0; elim H; clear H; generalize H1; unfold Rabs in |- *; + case (Rcase_abs x); intros; auto. +clear r H1; generalize (Rplus_eq_compat_l x 0 (- x) H0); + rewrite (let (H1, H2) := Rplus_ne x in H1); rewrite (Rplus_opp_r x); + trivial. +Qed. + +(*********) +Lemma Rabs_minus_sym : forall x y:R, Rabs (x - y) = Rabs (y - x). +intros; unfold Rabs in |- *; case (Rcase_abs (x - y)); + case (Rcase_abs (y - x)); intros. + generalize (Rminus_lt y x r); generalize (Rminus_lt x y r0); intros; + generalize (Rlt_asym x y H); intro; elimtype False; + auto. +rewrite (Ropp_minus_distr x y); trivial. +rewrite (Ropp_minus_distr y x); trivial. +unfold Rge in r, r0; elim r; elim r0; intros; clear r r0. +generalize (Ropp_lt_gt_0_contravar (x - y) H); rewrite (Ropp_minus_distr x y); + intro; unfold Rgt in H0; generalize (Rlt_asym 0 (y - x) H0); + intro; elimtype False; auto. +rewrite (Rminus_diag_uniq x y H); trivial. +rewrite (Rminus_diag_uniq y x H0); trivial. +rewrite (Rminus_diag_uniq y x H0); trivial. +Qed. + +(*********) +Lemma Rabs_mult : forall x y:R, Rabs (x * y) = Rabs x * Rabs y. +intros; unfold Rabs in |- *; case (Rcase_abs (x * y)); case (Rcase_abs x); + case (Rcase_abs y); intros; auto. +generalize (Rmult_lt_gt_compat_neg_l y x 0 r r0); intro; + rewrite (Rmult_0_r y) in H; generalize (Rlt_asym (x * y) 0 r1); + intro; unfold Rgt in H; elimtype False; rewrite (Rmult_comm y x) in H; + auto. +rewrite (Ropp_mult_distr_l_reverse x y); trivial. +rewrite (Rmult_comm x (- y)); rewrite (Ropp_mult_distr_l_reverse y x); + rewrite (Rmult_comm x y); trivial. +unfold Rge in r, r0; elim r; elim r0; clear r r0; intros; unfold Rgt in H, H0. +generalize (Rmult_lt_compat_l x 0 y H H0); intro; rewrite (Rmult_0_r x) in H1; + generalize (Rlt_asym (x * y) 0 r1); intro; elimtype False; + auto. +rewrite H in r1; rewrite (Rmult_0_l y) in r1; generalize (Rlt_irrefl 0); + intro; elimtype False; auto. +rewrite H0 in r1; rewrite (Rmult_0_r x) in r1; generalize (Rlt_irrefl 0); + intro; elimtype False; auto. +rewrite H0 in r1; rewrite (Rmult_0_r x) in r1; generalize (Rlt_irrefl 0); + intro; elimtype False; auto. +rewrite (Rmult_opp_opp x y); trivial. +unfold Rge in r, r1; elim r; elim r1; clear r r1; intros; unfold Rgt in H0, H. +generalize (Rmult_lt_compat_l y x 0 H0 r0); intro; + rewrite (Rmult_0_r y) in H1; rewrite (Rmult_comm y x) in H1; + generalize (Rlt_asym (x * y) 0 H1); intro; elimtype False; + auto. +generalize (Rlt_dichotomy_converse x 0 (or_introl (x > 0) r0)); + generalize (Rlt_dichotomy_converse y 0 (or_intror (y < 0) H0)); + intros; generalize (Rmult_integral x y H); intro; + elim H3; intro; elimtype False; auto. +rewrite H0 in H; rewrite (Rmult_0_r x) in H; unfold Rgt in H; + generalize (Rlt_irrefl 0); intro; elimtype False; + auto. +rewrite H0; rewrite (Rmult_0_r x); rewrite (Rmult_0_r (- x)); trivial. +unfold Rge in r0, r1; elim r0; elim r1; clear r0 r1; intros; + unfold Rgt in H0, H. +generalize (Rmult_lt_compat_l x y 0 H0 r); intro; rewrite (Rmult_0_r x) in H1; + generalize (Rlt_asym (x * y) 0 H1); intro; elimtype False; + auto. +generalize (Rlt_dichotomy_converse y 0 (or_introl (y > 0) r)); + generalize (Rlt_dichotomy_converse 0 x (or_introl (0 > x) H0)); + intros; generalize (Rmult_integral x y H); intro; + elim H3; intro; elimtype False; auto. +rewrite H0 in H; rewrite (Rmult_0_l y) in H; unfold Rgt in H; + generalize (Rlt_irrefl 0); intro; elimtype False; + auto. +rewrite H0; rewrite (Rmult_0_l y); rewrite (Rmult_0_l (- y)); trivial. +Qed. + +(*********) +Lemma Rabs_Rinv : forall r, r <> 0 -> Rabs (/ r) = / Rabs r. +intro; unfold Rabs in |- *; case (Rcase_abs r); case (Rcase_abs (/ r)); auto; + intros. +apply Ropp_inv_permute; auto. +generalize (Rinv_lt_0_compat r r1); intro; unfold Rge in r0; elim r0; intros. +unfold Rgt in H1; generalize (Rlt_asym 0 (/ r) H1); intro; elimtype False; + auto. +generalize (Rlt_dichotomy_converse (/ r) 0 (or_introl (/ r > 0) H0)); intro; + elimtype False; auto. +unfold Rge in r1; elim r1; clear r1; intro. +unfold Rgt in H0; generalize (Rlt_asym 0 (/ r) (Rinv_0_lt_compat r H0)); + intro; elimtype False; auto. +elimtype False; auto. +Qed. + +Lemma Rabs_Ropp : forall x:R, Rabs (- x) = Rabs x. +intro; cut (- x = -1 * x). +intros; rewrite H. +rewrite Rabs_mult. +cut (Rabs (-1) = 1). +intros; rewrite H0. +ring. +unfold Rabs in |- *; case (Rcase_abs (-1)). +intro; ring. +intro H0; generalize (Rge_le (-1) 0 H0); intros. +generalize (Ropp_le_ge_contravar 0 (-1) H1). +rewrite Ropp_involutive; rewrite Ropp_0. +intro; generalize (Rgt_not_le 1 0 Rlt_0_1); intro; generalize (Rge_le 0 1 H2); + intro; elimtype False; auto. +ring. +Qed. + +(*********) +Lemma Rabs_triang : forall a b:R, Rabs (a + b) <= Rabs a + Rabs b. +intros a b; unfold Rabs in |- *; case (Rcase_abs (a + b)); case (Rcase_abs a); + case (Rcase_abs b); intros. +apply (Req_le (- (a + b)) (- a + - b)); rewrite (Ropp_plus_distr a b); + reflexivity. +(**) +rewrite (Ropp_plus_distr a b); apply (Rplus_le_compat_l (- a) (- b) b); + unfold Rle in |- *; unfold Rge in r; elim r; intro. +left; unfold Rgt in H; generalize (Rplus_lt_compat_l (- b) 0 b H); intro; + elim (Rplus_ne (- b)); intros v w; rewrite v in H0; + clear v w; rewrite (Rplus_opp_l b) in H0; apply (Rlt_trans (- b) 0 b H0 H). +right; rewrite H; apply Ropp_0. +(**) +rewrite (Ropp_plus_distr a b); rewrite (Rplus_comm (- a) (- b)); + rewrite (Rplus_comm a (- b)); apply (Rplus_le_compat_l (- b) (- a) a); + unfold Rle in |- *; unfold Rge in r0; elim r0; intro. +left; unfold Rgt in H; generalize (Rplus_lt_compat_l (- a) 0 a H); intro; + elim (Rplus_ne (- a)); intros v w; rewrite v in H0; + clear v w; rewrite (Rplus_opp_l a) in H0; apply (Rlt_trans (- a) 0 a H0 H). +right; rewrite H; apply Ropp_0. +(**) +elimtype False; generalize (Rplus_ge_compat_l a b 0 r); intro; + elim (Rplus_ne a); intros v w; rewrite v in H; clear v w; + generalize (Rge_trans (a + b) a 0 H r0); intro; clear H; + unfold Rge in H0; elim H0; intro; clear H0. +unfold Rgt in H; generalize (Rlt_asym (a + b) 0 r1); intro; auto. +absurd (a + b = 0); auto. +apply (Rlt_dichotomy_converse (a + b) 0); left; assumption. +(**) +elimtype False; generalize (Rplus_lt_compat_l a b 0 r); intro; + elim (Rplus_ne a); intros v w; rewrite v in H; clear v w; + generalize (Rlt_trans (a + b) a 0 H r0); intro; clear H; + unfold Rge in r1; elim r1; clear r1; intro. +unfold Rgt in H; generalize (Rlt_trans (a + b) 0 (a + b) H0 H); intro; + apply (Rlt_irrefl (a + b)); assumption. +rewrite H in H0; apply (Rlt_irrefl 0); assumption. +(**) +rewrite (Rplus_comm a b); rewrite (Rplus_comm (- a) b); + apply (Rplus_le_compat_l b a (- a)); apply (Rminus_le a (- a)); + unfold Rminus in |- *; rewrite (Ropp_involutive a); + generalize (Rplus_lt_compat_l a a 0 r0); clear r r1; + intro; elim (Rplus_ne a); intros v w; rewrite v in H; + clear v w; generalize (Rlt_trans (a + a) a 0 H r0); + intro; apply (Rlt_le (a + a) 0 H0). +(**) +apply (Rplus_le_compat_l a b (- b)); apply (Rminus_le b (- b)); + unfold Rminus in |- *; rewrite (Ropp_involutive b); + generalize (Rplus_lt_compat_l b b 0 r); clear r0 r1; + intro; elim (Rplus_ne b); intros v w; rewrite v in H; + clear v w; generalize (Rlt_trans (b + b) b 0 H r); + intro; apply (Rlt_le (b + b) 0 H0). +(**) +unfold Rle in |- *; right; reflexivity. +Qed. + +(*********) +Lemma Rabs_triang_inv : forall a b:R, Rabs a - Rabs b <= Rabs (a - b). +intros; apply (Rplus_le_reg_l (Rabs b) (Rabs a - Rabs b) (Rabs (a - b))); + unfold Rminus in |- *; rewrite <- (Rplus_assoc (Rabs b) (Rabs a) (- Rabs b)); + rewrite (Rplus_comm (Rabs b) (Rabs a)); + rewrite (Rplus_assoc (Rabs a) (Rabs b) (- Rabs b)); + rewrite (Rplus_opp_r (Rabs b)); rewrite (proj1 (Rplus_ne (Rabs a))); + replace (Rabs a) with (Rabs (a + 0)). + rewrite <- (Rplus_opp_r b); rewrite <- (Rplus_assoc a b (- b)); + rewrite (Rplus_comm a b); rewrite (Rplus_assoc b a (- b)). + exact (Rabs_triang b (a + - b)). + rewrite (proj1 (Rplus_ne a)); trivial. +Qed. + +(* ||a|-|b||<=|a-b| *) +Lemma Rabs_triang_inv2 : forall a b:R, Rabs (Rabs a - Rabs b) <= Rabs (a - b). +cut + (forall a b:R, Rabs b <= Rabs a -> Rabs (Rabs a - Rabs b) <= Rabs (a - b)). +intros; destruct (Rtotal_order (Rabs a) (Rabs b)) as [Hlt| [Heq| Hgt]]. +rewrite <- (Rabs_Ropp (Rabs a - Rabs b)); rewrite <- (Rabs_Ropp (a - b)); + do 2 rewrite Ropp_minus_distr. +apply H; left; assumption. +rewrite Heq; unfold Rminus in |- *; rewrite Rplus_opp_r; rewrite Rabs_R0; + apply Rabs_pos. +apply H; left; assumption. +intros; replace (Rabs (Rabs a - Rabs b)) with (Rabs a - Rabs b). +apply Rabs_triang_inv. +rewrite (Rabs_right (Rabs a - Rabs b)); + [ reflexivity + | apply Rle_ge; apply Rplus_le_reg_l with (Rabs b); rewrite Rplus_0_r; + replace (Rabs b + (Rabs a - Rabs b)) with (Rabs a); + [ assumption | ring ] ]. +Qed. + +(*********) +Lemma Rabs_def1 : forall x a:R, x < a -> - a < x -> Rabs x < a. +unfold Rabs in |- *; intros; case (Rcase_abs x); intro. +generalize (Ropp_lt_gt_contravar (- a) x H0); unfold Rgt in |- *; + rewrite Ropp_involutive; intro; assumption. +assumption. +Qed. + +(*********) +Lemma Rabs_def2 : forall x a:R, Rabs x < a -> x < a /\ - a < x. +unfold Rabs in |- *; intro x; case (Rcase_abs x); intros. +generalize (Ropp_gt_lt_0_contravar x r); unfold Rgt in |- *; intro; + generalize (Rlt_trans 0 (- x) a H0 H); intro; split. +apply (Rlt_trans x 0 a r H1). +generalize (Ropp_lt_gt_contravar (- x) a H); rewrite (Ropp_involutive x); + unfold Rgt in |- *; trivial. +fold (a > x) in H; generalize (Rgt_ge_trans a x 0 H r); intro; + generalize (Ropp_lt_gt_0_contravar a H0); intro; fold (0 > - a) in |- *; + generalize (Rge_gt_trans x 0 (- a) r H1); unfold Rgt in |- *; + intro; split; assumption. +Qed. + +Lemma RmaxAbs : + forall (p q:R) r, p <= q -> q <= r -> Rabs q <= Rmax (Rabs p) (Rabs r). +intros p q r H' H'0; case (Rle_or_lt 0 p); intros H'1. +repeat rewrite Rabs_right; auto with real. +apply Rle_trans with r; auto with real. +apply RmaxLess2; auto. +apply Rge_trans with p; auto with real; apply Rge_trans with q; + auto with real. +apply Rge_trans with p; auto with real. +rewrite (Rabs_left p); auto. +case (Rle_or_lt 0 q); intros H'2. +repeat rewrite Rabs_right; auto with real. +apply Rle_trans with r; auto. +apply RmaxLess2; auto. +apply Rge_trans with q; auto with real. +rewrite (Rabs_left q); auto. +case (Rle_or_lt 0 r); intros H'3. +repeat rewrite Rabs_right; auto with real. +apply Rle_trans with (- p); auto with real. +apply RmaxLess1; auto. +rewrite (Rabs_left r); auto. +apply Rle_trans with (- p); auto with real. +apply RmaxLess1; auto. +Qed. + +Lemma Rabs_Zabs : forall z:Z, Rabs (IZR z) = IZR (Zabs z). +intros z; case z; simpl in |- *; auto with real. +apply Rabs_right; auto with real. +intros p0; apply Rabs_right; auto with real zarith. +intros p0; rewrite Rabs_Ropp. +apply Rabs_right; auto with real zarith. +Qed. +
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