%% 
%%  Example 01-04-4 
%%  Copyright (C) 2017 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{304.62788pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{array,mathtools}
%StopShownPreambleCommands
\begin{document}
\fboxsep=0pt
\def\xstrut{\vphantom{\int\frac{x}{x}}}
\[
\begin{array}{rcl}
\boxed{f(x)\xstrut} & \boxed{\xstrut=} & \boxed{\int\frac{\sin x}{x}\,\mathrm{d}x}
\end{array}
\]
%
\[
\arraycolsep=1.4pt
\begin{array}{rcl}
\boxed{f(x)\xstrut} & \boxed{\xstrut=} & \boxed{\int\frac{\sin x}{x}\,\mathrm{d}x}
\end{array}
\]
\end{document}
