Merged changes from the 1.5.2p2 release.
(Very rough.)
diff --git a/Doc/lib/libmath.tex b/Doc/lib/libmath.tex
index 0a45fb3..af1ac10 100644
--- a/Doc/lib/libmath.tex
+++ b/Doc/lib/libmath.tex
@@ -5,7 +5,19 @@
\modulesynopsis{Mathematical functions (\function{sin()} etc.).}
This module is always available. It provides access to the
-mathematical functions defined by the C standard. They are:
+mathematical functions defined by the C standard.
+
+These functions cannot be used with complex numbers; use the functions
+of the same name from the \refmodule{cmath} module if you require
+support for complex numbers. The distinction between functions which
+support complex numbers and those which don't is made since most users
+do not want to learn quite as much mathematics as required to
+understand complex numbers. Receiving an exception instead of a
+complex result allows earlier detection of the unexpected complex
+number used as a parameter, so that the programmer can determine how
+and why it was generated in the first place.
+
+The following functions provided by this module:
\begin{funcdesc}{acos}{x}
Return the arc cosine of \var{x}.