%%
%% The LaTeX Companion, 2ed (second printing August 2004)
%%
%% Example 8-7-6 on page 506.
%%
%% 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{159.0pt}

\StartShownPreambleCommands
\usepackage{amsmath}
\StopShownPreambleCommands
\begin{document}
\[
  f_p (x) =
  \begin{cases}
    \frac{1}{\smash[b]{p}}                & x = p  \\
    \frac{\strut
          \smash[t]{\frac{(1 - x)^{\frac{1}{2}} }
                         { x - \sin (x - p)     } } }
         {\sqrt{1 - p} \, \cos (x - p)}   & x \neq p
  \end{cases}
\]
\end{document}