\setlength{\unitlength}{1cm}
\begin{center}
\begin{Picture}(-7,-2.5)(7,2.5)
{\referencesystem(0,0)(\numberHALFPI,0)(0,1)
\renewcommand{\xunitdivisions}{2}
\renewcommand{\yunitdivisions}{2}
\makenolabels
\renewcommand{\Pictlabelsep}{0.25}
\cartesianaxes(-4.2,-2.2)(4.2,2.2)

\printylabels{-2}{0.5}{2}

\highestlabel{$-3\pi/2$}
\printxlabel{-4}{-2\pi}
\printxlabel{-3}{-3\pi/2}
\printxlabel{-2}{-\pi}
\printxlabel{-1}{-\pi/2}
\printxlabel{1}{\pi/2}
\printxlabel{2}{\pi}
\printxlabel{3}{3\pi/2}
\printxlabel{4}{2\pi}
}
\end{Picture}
\end{center}
