\input{preamble-standalone.ltx} \begin{document} % Ex. No. 126 (Section 19.1.9 : Orthogonal circle passing through two given points) \begin{tikzpicture}[scale=1] \tkzDefPoint(0,0){O} \tkzDefPoint(1,0){A} \tkzDrawCircle(O,A) \tkzDefPoint(-1.5,-1.5){z1} \tkzDefPoint(1.5,-1.25){z2} \tkzDefCircle[orthogonal through=z1 and z2](O,A) \tkzGetPoint{c} \tkzDrawCircle[thick,color=red](tkzPointResult,z1) \tkzDrawPoints[fill=red,color=black, size=4](O,A,z1,z2,c) \tkzLabelPoints(O,A,z1,z2,c) \end{tikzpicture} \end{document}