\documentclass[12pt,a4paper]{article}
\usepackage[francais]{babel}
\usepackage{mafr}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{lmodern}
\usepackage[dvipsnames]{xcolor}
\usepackage{pstricks}
\usepackage{pst-eucl}
\begin{document}
\begin{footnotesize}
\begin{pspicture*}(0,0)(8,6)%
\psset{PointNameSep=.8em,linewidth=.5pt,RightAngleType=suisseromand}%
\pstGeonode(3,2){A}(6,4){B}(4,5){P}(1,3){Q}%
\pcline[nodesep=-10](A)(B)%
\pstProjection[CodeFig=true]{A}{B}{P}%
\pstProjection[PosAngle=80]{A}{B}{Q}[R]%
\pcline[nodesep=-10,linecolor=red](Q)(R)%
\end{pspicture*}
\end{footnotesize}
\end{document}
