%% 
%%  Ein Beispiel der DANTE-Edition
%%  Mathematiksatz mit LaTeX
%%  3. Auflage
%%  Beispiel 10-09-7 auf Seite 231.
%%  Copyright (C) 2018 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[10pt]{screxa}
\pagestyle{empty}
\setlength\textwidth{146.40707pt}
\AtBeginDocument{\setlength\parindent{0pt}}
%StartShownPreambleCommands
\usepackage{amsmath}
%StopShownPreambleCommands
\begin{document}
\begin{tabular}{l}
$\tan\alpha=\dfrac{\sin\alpha}
  {\cos\alpha} $\\
$\tan2\alpha=\dfrac{2\tan\alpha}
  {1-\tan^2\alpha} $\\
$\tan3\alpha=\dfrac{3\tan\alpha-\tan^3\alpha}
  {1-3\tan^2\alpha} $
\end{tabular}
\end{document}