correct typo; document sys.platform
diff --git a/Doc/lib/libsys.tex b/Doc/lib/libsys.tex
index 8899052..ff5d65e 100644
--- a/Doc/lib/libsys.tex
+++ b/Doc/lib/libsys.tex
@@ -52,7 +52,7 @@
This value is not actually defined by the module, but can be set by
the user (or by a program) to specify a clean-up action at program
exit. When set, it should be a parameterless function. This function
- will be called when the interpreter exits in any way (except not when a
+ will be called when the interpreter exits in any way (except when a
fatal error occurs: in that case the interpreter's internal state
cannot be trusted).
\end{datadesc}
@@ -81,6 +81,11 @@
installation-dependent default.
\end{datadesc}
+\begin{datadesc}{platform}
+This string contains a platform identifier. This can be used to
+append platform-specific components to \code{sys.path}, for instance.
+\end{datadesc}
+
\begin{datadesc}{ps1}
\dataline{ps2}
Strings specifying the primary and secondary prompt of the