%% 
%%  Ein Beispiel der DANTE-Edition
%%  Mathematiksatz mit LaTeX
%%  3. Auflage
%%  Beispiel 04-20-6 auf Seite 75.
%%  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{352.81416pt}
\AtBeginDocument{\setlength\parindent{0pt}}
%StartShownPreambleCommands
\newcommand*\diff[1][]{\mathop{}\!\mathrm{d}\if\relax\detokenize{#1}\relax\else^{#1}\mkern-1.4mu\fi}
%StopShownPreambleCommands
\begin{document}
\[
ay^{\prime}=a\frac{\diff y}{\diff x}
  \quad c\cdot v =  c\,\frac{\diff s}{\diff t}
  \quad a = \frac{\diff[2]t}{\diff[2]t}
  \quad \int\!\!\diff y=\int\!\sin(x)\diff x
\]
\end{document}