 \begin{tikzpicture}[scale=1]
 \tkzDefPoint(0,4){A}
 \tkzDefPoint(2,2){B}
 \tkzDefMidPoint(A,B) \tkzGetPoint{I}
 \tkzDefRandPointOn[segment = I--B]
  \tkzGetPoint{C}
 \tkzDefCircle[through](A,C)
 \tkzGetLength{rACpt}
 \tkzpttocm(\rACpt){rACcm}
 \tkzDrawCircle(A,C)
 \tkzDrawPoints(A,B,C)
 \tkzLabelPoints(A,B,C)
 \tkzLabelCircle[draw,fill=Gold,%
 text width=3cm,text centered,
 font=\scriptsize](A,C)(-90)%
 {La mesure du rayon est :
  \rACpt pt soit \rACcm cm}
 \end{tikzpicture}
