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

% Ex. No. 72 (Section 13.1.5 : Drawing a tangent option \tkzimp{from with R} and \tkzimp{at})

  \begin{tikzpicture}[scale=.5]
  \tkzDefPoint(0,0){O}
  \tkzDefPoint(6,6){E}
  \tkzDefRandPointOn[circle=center O radius 4cm]
  \tkzGetPoint{A}
  \tkzDefRandPointOn[circle=center O radius 4cm]
  \tkzGetPoint{B}
  \tkzDrawSegments(O,A O,B)
  \tkzDrawCircle(O,A)
  \tkzDefTangent[from with R=E](O,4cm)
  \tkzGetSecondPoint{k}
  \tkzDefTangent[at=A](O)
  \tkzGetPoint{h}
  \tkzDrawPoints(E)
  \tkzDrawLine[add = .5 and .5](A,h)
  \tkzDrawLine[add = .5 and .5](E,k)
  \tkzMarkRightAngle[fill=red!30](O,A,h)
\end{tikzpicture}

\end{document}
