%% 
%%  An UIT Edition example
%% 
%%  Example 10-09-7 on page 218.
%% 
%%  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
%% 
\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{177.70511pt}
\AtBeginDocument{\setlength\parindent{0pt}}
\StartShownPreambleCommands
\usepackage{amsmath}
\renewcommand\arraystretch{2.2}
\StopShownPreambleCommands
\begin{document}
\begin{tabular}{|l|}\hline
$\tan\alpha=\dfrac{\sin\alpha}
  {\cos\alpha} $\\
$\tan2\alpha=\dfrac{2\tan\alpha}
  {1-\tan^2\alpha} $\\
\rule[-3ex]{0pt}{6ex}%
$\tan3\alpha=\dfrac{3\tan\alpha-\tan^3\alpha}
  {1-3\tan^2\alpha} $\\\hline
\end{tabular}
\end{document}
