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

% Ex. No. 84 (Section 10.4 : tkzSaveBB}{)

\begin{tikzpicture}
 \begin{scope}
   \tkzSetBB(0,0)(6,2) \tkzShowBB[fill=blue!20]
   \tkzSaveBB
 \end{scope}
  \tkzDefPoint(3,3){A}\tkzShowBB
  \tkzDrawCircle[R,fill=yellow,opacity=.2](A,2cm)
  \tkzRestoreBB
\end{tikzpicture}

\end{document}