\begin{tikzpicture}[scale=1.25] \tkzDefPoint(2,1){O} \tkzDefRandPointOn[circle=center O radius 1.5cm]{A} \tkzDrawCircle(O,A) \tkzDefPointBy[rotation=center O angle 100](A) \tkzGetPoint{C} \tkzDefPointBy[rotation=center O angle 78](A) \tkzGetPoint{B} \tkzDrawPoints(O,A,B,C) \tkzDrawSegments(C,B B,A A,O O,C) \tkzDefCentroid(A,B,C,O) \tkzDrawPoint(tkzPointResult) \tkzAutoLabelPoints[center=tkzPointResult, dist=.3,red](O,A,B,C) \end{tikzpicture}