\input{preamble-standalone.ltx} \begin{document} % Ex. No. 219 (Section 27.1.2 : Example of \tkzcname{tkzShowLine} and \tkzname{perpendicular}) \begin{tikzpicture} \tkzDefPoints{0/0/A, 3/2/B, 2/2/C} \tkzDefLine[perpendicular=through C,K=-.5](A,B) \tkzGetPoint{c} \tkzShowLine[perpendicular=through C,K=-.5,gap=3](A,B) \tkzDefPointBy[projection=onto A--B](c)\tkzGetPoint{h} \tkzMarkRightAngle[fill=lightgray](A,h,C) \tkzDrawLines[add=.5 and .5](A,B C,c) \tkzDrawPoints(A,B,C,h,c) \end{tikzpicture} \end{document}