% prosperdemo.tex,v 1.2 2002/11/14 20:46:00 hansfn Exp
%  
% TeXPower bundle - dynamic online presentations with LaTeX
% Copyright (C) 1999-2002 Stephan Lehmke
% 
% This program is free software; you can redistribute it and/or
% modify it under the terms of the GNU General Public License
% as published by the Free Software Foundation; either version 2
% of the License, or (at your option) any later version.
% 
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
%
\documentclass[pdf,colorBG,slideColor,azure]{prosper}
\usepackage[display]{texpower}
\begin{document}
\stepwise[\boxedsteps]
{%
\begin{slide}{An aligned equation}
  \begin{eqnarray}
    \step{\sum_{i=1}^{n} i} & \step{=} & \restep{1 + 2 + \cdots + (n-1) + n}\\
    %
                     & \step{=} & \restep{1 + n + 2 + (n-1) + \cdots}\\
    %
                     & \step{=} & \restep
                                  {% 
                                    \switch
                                    {%
                                      \vphantom{\underbrace{(1 + n) + \cdots + (1 + n)}_{\times\frac{n}{2}}}%
                                      (1 + n) + \cdots + (1 + n)%
                                      }
                                    {\underbrace{(1 + n) + \cdots + (1 + n)}_{\times\frac{n}{2}}}%
                                    }
                                  \\
    %
                     & \step{=} & \restep{\frac{(1 + n)\step{{}\cdot n}}{\restep{2}}}
  \end{eqnarray}
\end{slide}
}


\end{document}

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