%% 
%%  Example 01-03-8 
%%  Copyright (C) 2017 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{134.31393pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{amsmath}
%StopShownPreambleCommands
\begin{document}
\fbox{\parbox{\dimexpr\linewidth-2\fboxsep-2\fboxrule}{%
  \begin{equation}
    f(x)=\int_1^{\infty}\dfrac{1}{x^2}\,\mathrm{d}x=1
  \end{equation}%
}}
\end{document}
