%% 
%%  An UIT Edition example
%% 
%%  Example 04-18-11 on page 68.
%% 
%%  Copyright (C) 2010 Herbert Voss
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{375.57637pt}
\AtBeginDocument{\setlength\parindent{0pt}}
\StartShownPreambleCommands
\let\itemOld\item\makeatletter
\renewcommand\item[1][]{\def\@tempa{#1}%
  \ifx\@tempa\@empty\itemOld\else\boldmath\itemOld[#1]\unboldmath\fi}
\newcommand\Section[2][]{\def\@tempa{#1}
  \protect\boldmath\ifx\@tempa\@empty\section[#2]{#2}\else
    \section[#1]{#2}\fi\protect\unboldmath} \makeatother
\StopShownPreambleCommands
\begin{document}
\Section{Function $f(x)=x^2$}
\begin{description}
  \item[This is $y=f(x)$] only a demonstration.
  \item[And $z=f(x,y)$] another demonstration.
\end{description}
\end{document}