a little more detail on the functions motivation

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@233074 c90b9560-bf6c-de11-be94-00142212c4b1

reference/math/functions/log1p.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.9 $ -->
+<!-- $Revision: 1.10 $ -->
 <refentry id='function.log1p'>
  <refnamediv>
   <refname>log1p</refname>
@@ -19,6 +19,8 @@
    <function>log1p</function> returns log(1 +
    <parameter>number</parameter>) computed in a way that is accurante even
    when the value of <parameter>number</parameter> is close to zero.
+   <function>log</function> might only return log(1) in this case
+   due to lack of precision.
   </para>
   &note.no-windows;
  </refsect1>