%% 
%%  The LaTeX Graphics Companion, 2ed (first printing May 2007)
%% 
%%  Example 6-2-3 on page 336.
%% 
%%  Copyright (C) 2007 Michel Goossens, Frank Mittelbach, Denis Roegel, Sebastian Rahtz, Herbert Vo\ss 
%% 
%%  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.
%% 

\documentclass{ttctexa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{207.83385pt}
\StartShownPreambleCommands
\usepackage{pstricks,pst-node}
\SpecialCoor
\newcommand\DefNodes[2]{%
  \rnode[tl]{#1-tl}{%
     \rnode[tr]{#1-tr}{%
        \rnode[bl]{#1-bl}{%
           \rnode[br]{#1-br}{#2}}}}}
\StopShownPreambleCommands
\begin{document}
  \huge\[
  \frac{\DefNodes{A}{A_1}+\DefNodes{B}{B_1}+C_1}
     {\DefNodes{D}{D_1}+\DefNodes{E}{E_1}+\DefNodes{F}{F_1}} \]
  \psccurve[linecolor=blue,linestyle=dashed,%
    fillstyle=hlines,hatchcolor=black!20]
      (D-bl)(A-tl)(A-tr)([angle=-90,nodesep=0.1]B-bl)
      ([angle=-90,nodesep=0.1]B-br)(F-tr)(F-br)(F-bl)
      ([angle=90,nodesep=0.1]E-tr)([angle=90,nodesep=0.1]E-tl)
      (D-br)(D-bl)
\end{document}