%%
%% The LaTeX Companion, 2ed (second printing August 2004)
%%
%% Example 8-4-2 on page 490.
%%
%% Copyright (C) 2004 Frank Mittelbach, Michel Goossens,
%%    Johannes Braams, David Carlisle, and Chris Rowley
%%
%% 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{207.0pt}

\StartShownPreambleCommands
\usepackage{amsmath}
\StopShownPreambleCommands
\begin{document}
\begin{equation*}
\cfrac {1}{\sqrt{2} +
 \cfrac {1}{\sqrt{3} +
  \cfrac {1}{\sqrt{4} +
   \cfrac[r] {1}{\sqrt{5} +
    \cfrac[l] {1}{\sqrt{6} + \dotsb }
   }}}}
\end{equation*}
\end{document}