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%%  Example 02-10-1 
%%  Copyright (C) 2016 Herbert Voss
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\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{328.62788pt}
\setlength\parindent{0pt}
\usepackage[T1]{fontenc}
\usepackage{kpfonts}
%StartShownPreambleCommands
\usepackage{amsmath}
%StopShownPreambleCommands
\begin{document}
\begin{align}
f(x) & =a\tag{linear}\label{eq:linear}\\
g(x) & =\,\mathrm{d}x^{2}+cx+b\tag{quadratic}\label{eq:quadratic}\\
h(x) & =\sin x\tag*{trigonometric}
\end{align}
Eq.~\ref{eq:linear} is a linear and eq.~\ref{eq:quadratic} is a quadratic function.
\end{document}
