1 files changed, 18 insertions, 10 deletions
diff --git a/src/elementaryFunctions/cosh/dcoshs.c b/src/elementaryFunctions/cosh/dcoshs.c
index 83769292..78131389 100644
--- a/src/elementaryFunctions/cosh/dcoshs.c
+++ b/src/elementaryFunctions/cosh/dcoshs.c
@@ -1,18 +1,26 @@
 /*
-**  -*- C -*-
-**
-** dcoshs.c
-** Made by  Bruno JOFRET <bruno.jofret@inria.fr>
-**
-** Started on  Thu Dec  7 12:02:41 2006 jofret
-** Last update Fri Apr 20 14:40:59 2007 jofret
-**
-** Copyright INRIA 2006
+ *  Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
+ *  Copyright (C) 2008-2008 - INRIA - Bruno JOFRET
+ *
+ *  This file must be used under the terms of the CeCILL.
+ *  This source file is licensed as described in the file COPYING, which
+ *  you should have received as part of this distribution.  The terms
+ *  are also available at
+ *  http://www.cecill.info/licences/Licence_CeCILL_V2-en.txt
+ *
+ */
+
+/*
+//         cosh(z) = 0.5 (exp(|z|) + exp(-|z|))
+//                 = 0.5 ( y + 1/y ) with y = exp(|z|)
 */
 
 #include <math.h>
 #include "cosh.h"
+#include "exp.h"
+#include "abs.h"
 
 double	       dcoshs(double x) {
-  return (cosh(x));
+  double y = dexps(dabss(x));
+  return (0.5 * (y + 1.0/y));
 }