%%
%% An UIT Edition example
%%
%% Example 09-09-2 on page 175.
%%
%% Copyright (C) 2010 Herbert Voss
%%
%% 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.
%%
%%
%% ====
% Show page(s) 1
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\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{375.57637pt}
\AtBeginDocument{\setlength\parindent{0pt}}
\setcounter{equation}{3}
\renewcommand\theequation{9.\arabic{equation}}
\StartShownPreambleCommands
\usepackage{cases}
\StopShownPreambleCommands
\begin{document}
\begin{subnumcases}{\label{w} w\equiv}
0 & $c = d = 0$\label{wzero}\\
\sqrt{|c|}\,\sqrt{\frac{1 + \sqrt{1+(d/c)^2}}{2}} & $|c| \geq |d|$ \\
\sqrt{|d|}\,\sqrt{\frac{|c/d| + \sqrt{1+(c/d)^2}}{2}} & $|c| < |d|$
\end{subnumcases}
\begin{subnumcases}{\sqrt{c+id}=}
0 & $w=0$ (case \ref{wzero}) \\
w+i\frac{d}{2w} & $w \neq 0$, $c \geq 0$ \\
\frac{|d|}{2w} + iw \qquad & $w \neq 0$, $c < 0$, $d \geq 0$\\
\frac{|d|}{2w} - iw \qquad & $w \neq 0$, $c < 0$, $d < 0$
\end{subnumcases}
\end{document}
