\input{preamble-standalone.ltx} \begin{document} % Ex. No. 149 (Section 18.1.10 : Orthogonal circle of given center) \begin{tikzpicture}[scale=.75] \tkzDefPoints{0/0/O,1/0/A} \tkzDefPoints{1.5/1.25/B,-2/-3/C} \tkzDefCircle[orthogonal from=B](O,A) \tkzGetPoints{z1}{z2} \tkzDefCircle[orthogonal from=C](O,A) \tkzGetPoints{t1}{t2} \tkzDrawCircle(O,A) \tkzDrawCircle[thick,color=red](B,z1) \tkzDrawCircle[thick,color=red](C,t1) \tkzDrawPoints(t1,t2,C) \tkzDrawPoints(z1,z2,O,A,B) \tkzLabelPoints(O,A,B,C) \end{tikzpicture} \end{document}