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-rw-r--r--theories/Reals/Ranalysis4.v12
1 files changed, 12 insertions, 0 deletions
diff --git a/theories/Reals/Ranalysis4.v b/theories/Reals/Ranalysis4.v
index dd8e0dd52..2f097c4ae 100644
--- a/theories/Reals/Ranalysis4.v
+++ b/theories/Reals/Ranalysis4.v
@@ -13,6 +13,7 @@ Require Import Rtrigo1.
Require Import Ranalysis1.
Require Import Ranalysis3.
Require Import Exp_prop.
+Require Import MVT.
Local Open Scope R_scope.
(**********)
@@ -398,3 +399,14 @@ Proof.
intro; apply derive_pt_eq_0.
apply derivable_pt_lim_sinh.
Qed.
+
+Lemma sinh_lt : forall x y, x < y -> sinh x < sinh y.
+intros x y xy; destruct (MVT_cor2 sinh cosh x y xy) as [c [Pc _]].
+ intros; apply derivable_pt_lim_sinh.
+apply Rplus_lt_reg_l with (Ropp (sinh x)); rewrite Rplus_opp_l, Rplus_comm.
+unfold Rminus at 1 in Pc; rewrite Pc; apply Rmult_lt_0_compat;[ | ].
+ unfold cosh; apply Rmult_lt_0_compat;[|apply Rinv_0_lt_compat, Rlt_0_2].
+ now apply Rplus_lt_0_compat; apply exp_pos.
+now apply Rlt_Rminus; assumption.
+Qed.
+