\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}