From ba1358602769acf2989f419ba5995eef209ad202 Mon Sep 17 00:00:00 2001
From: John Maddock <john@johnmaddock.co.uk>
Date: Sat, 6 Oct 2012 16:53:15 +0000
Subject: [PATCH] Fix asinh and acosh to work with very large arguments without
 overflow.

[SVN r80884]
---
 include/boost/math/special_functions/acosh.hpp | 3 ++-
 include/boost/math/special_functions/asinh.hpp | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/boost/math/special_functions/acosh.hpp b/include/boost/math/special_functions/acosh.hpp
index 40ca985ed..5a43ae57d 100644
--- a/include/boost/math/special_functions/acosh.hpp
+++ b/include/boost/math/special_functions/acosh.hpp
@@ -21,6 +21,7 @@
 #include <boost/math/policies/error_handling.hpp>
 #include <boost/math/special_functions/math_fwd.hpp>
 #include <boost/math/special_functions/log1p.hpp>
+#include <boost/math/constants/constants.hpp>
 
 // This is the inverse of the hyperbolic cosine function.
 
@@ -58,7 +59,7 @@ namespace boost
                 {
                     // http://functions.wolfram.com/ElementaryFunctions/ArcCosh/06/01/06/01/0001/
                     // approximation by laurent series in 1/x at 0+ order from -1 to 0
-                    return( log( x * 2) );
+                    return log(x) + constants::ln_two<T>();
                 }
                 else if(x < 1.5f)
                 {
diff --git a/include/boost/math/special_functions/asinh.hpp b/include/boost/math/special_functions/asinh.hpp
index cf2a343e6..0534f550d 100644
--- a/include/boost/math/special_functions/asinh.hpp
+++ b/include/boost/math/special_functions/asinh.hpp
@@ -22,6 +22,7 @@
 #include <boost/math/special_functions/math_fwd.hpp>
 #include <boost/math/special_functions/sqrt1pm1.hpp>
 #include <boost/math/special_functions/log1p.hpp>
+#include <boost/math/constants/constants.hpp>
 
 // This is the inverse of the hyperbolic sine function.
 
@@ -52,7 +53,7 @@ namespace boost
                 {
                     // http://functions.wolfram.com/ElementaryFunctions/ArcSinh/06/01/06/01/0001/
                     // approximation by laurent series in 1/x at 0+ order from -1 to 1
-                    return log(x * 2) + 1/ (4 * x * x);
+                    return constants::ln_two<T>() + log(x) + 1/ (4 * x * x);
                 }
                 else if(x < 0.5f)
                 {