%% 
%%  An UIT Edition example
%% 
%%  Example 03-03-1 on page 21.
%% 
%%  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{177.70511pt}
\setlength\parindent{0pt}
\setcounter{equation}{12}
\renewcommand\theequation{3.\arabic{equation}}
\StartShownPreambleCommands
\makeatletter
\newcommand\be{\@ifstar{\[}{\equation}}
\newcommand\ee{\@ifstar{\]}{\endequation}}
\makeatother
\StopShownPreambleCommands
\begin{document}
\be  f(x)=\int\frac{\sin x}{x}\,\mathrm{d}x \ee
\be* f(x)=\int\frac{\sin x}{x}\,\mathrm{d}x \ee*
\end{document}