\input{preamble-standalone.ltx}
\begin{document}

% Ex. No. 150 (Section 19.1.1 : Circles and styles, draw a circle and color the disc)

\begin{tikzpicture}
  \tkzDefPoint(0,0){O}
  \tkzDefPoint(3,0){A}
  \tkzDrawCircle[color=blue](O,A)
  \tkzDrawCircle[diameter,color=red,%
                 line width=2pt,fill=red!40,%
                 opacity=.5](O,A)
  \edef\rayon{\fpeval{0.25*exp(1)}}
  \tkzDrawCircle[R,color=orange](O,\rayon cm)
\end{tikzpicture}

\end{document}