%% 
%%  A DANTE-Edition example
%% 
%% 
%%  Copyright (C) 2011 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[]{article}
\pagestyle{empty}
\setlength\textwidth{201.70511pt}
\setlength\parindent{0pt}
\makeatletter
\newcount\pst@cntm\newcount\pst@cntn\newcount\pst@cnto
\def\pst@mod#1#2#3{%
  \begingroup%
  \pst@cntm=#1\pst@cntn=#2\relax \pst@cnto=\pst@cntm
  \divide\pst@cntm by \pst@cntn  \multiply\pst@cntn by \pst@cntm
  \advance\pst@cnto by -\pst@cntn
  \edef\value{\endgroup\def\noexpand#3{\number\pst@cnto}}\value}
\makeatother

\usepackage{pstricks,pst-plot}
\makeatletter
\def\pst@@@hlabel#1{\small%
    \pst@mod{#1}{2}\tempa%              0 or 1
    \ifnum1>\tempa%                     odd value?
       \count1=#1\divide\count1 by 2%   #1/2
        $\the\count1\pi$%               n*pi
    \else$\frac{#1}{2}\pi$\fi}%         n/2*pi
\makeatother

\begin{document}
\begin{pspicture}(-0.5,-1.25)(10,1.25)
  \psaxes[xunit=1.570796,showorigin=false]{->}(0,0)(-0.5,-1.25)(6.4,1.25)
  \psplot[linecolor=red,linewidth=1.5pt]{0}{9.4247}{x RadtoDeg sin}
\end{pspicture}
\end{document}