Avec l’exemple "12.1.3 Example with orthogonal and parallel" de la documentation de l'extension `tkz-euclide` :
\documentclass{standalone}
\usepackage{tkz-euclide}
\begin{document}
\begin{tikzpicture}
\tkzDefPoints{-1.5/-0.25/A,1/-0.75/B,-0.7/1/C}
\tkzDrawLine(A,B)
\tkzDrawPoints(A,B,C)
\tkzDefLine[parallel=through C](A,B)
\tkzGetPoint{c'}
\tkzDrawLine(C,c')
\end{tikzpicture}
\end{document}\end{document}
![alt text][1]
[1]: https://texnique.fr/osqa/upfiles/document2_E1gIuaP.png
