diff options
Diffstat (limited to 'theories/Reals/Rbasic_fun.v')
-rw-r--r-- | theories/Reals/Rbasic_fun.v | 18 |
1 files changed, 7 insertions, 11 deletions
diff --git a/theories/Reals/Rbasic_fun.v b/theories/Reals/Rbasic_fun.v index fe5402e6e..df1662497 100644 --- a/theories/Reals/Rbasic_fun.v +++ b/theories/Reals/Rbasic_fun.v @@ -451,20 +451,16 @@ Qed. Lemma Rabs_Ropp : forall x:R, Rabs (- x) = Rabs x. Proof. - intro; cut (- x = -1 * x). - intros; rewrite H. + intro; replace (-x) with (-1 * x) by ring. rewrite Rabs_mult. - cut (Rabs (-1) = 1). - intros; rewrite H0. - ring. + replace (Rabs (-1)) with 1. + apply Rmult_1_l. unfold Rabs; 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; exfalso; auto. - ring. + rewrite <- Ropp_0. + intro H0; apply Ropp_ge_cancel in H0. + elim (Rge_not_lt _ _ H0). + apply Rlt_0_1. Qed. (*********) |