\input{preamble-standalone.ltx} \begin{document} % Ex. No. 49 (Section 11.1.1 : \tkzcname{tkzDefPointWith} et \tkzname{colinear at}) \begin{tikzpicture}[scale=1.2, vect/.style={->,shorten >=3pt,>=latex'}] \tkzDefPoint(2,3){A} \tkzDefPoint(4,2){B} \tkzDefPoint(0,1){C} \tkzDefPointWith[colinear=at C](A,B) \tkzGetPoint{D} \tkzDrawPoints[color=red](A,B,C,D) \tkzLabelPoints[above right=3pt](A,B,C,D) \tkzDrawSegments[vect](A,B C,D) \end{tikzpicture} \end{document}