\input{preamble-standalone.ltx} \begin{document} % Ex. No. 39 (Section 6.1.4 : Option \tkzname{in}) \begin{tikzpicture} \tkzDefPoints{0/1/A,3/2/B,1/4/C} \tkzDefTriangleCenter[in](A,B,C)\tkzGetPoint{I} \tkzDefPointBy[projection=onto A--C](I) \tkzGetPoint{Ib} \tkzDrawPolygon[color=blue](A,B,C) \tkzDrawPoints(A,B,C,I) \tkzDrawLines[add = 0 and 2/3](A,I B,I C,I) \tkzDrawCircle(I,Ib) \end{tikzpicture} \end{document}