tkz-euclide : un exemple tout simple

\documentclass{scrartcl}      
\usepackage[upright]{fourier} 
\usepackage[usenames,dvipsnames]{xcolor}
\usepackage{tkz-euclide} 
\definecolor{fondpaille}{cmyk}{0,0,0.1,0}
\pagecolor{fondpaille}   
\color{Maroon}  
\tkzSetUpColors[background=fondpaille,text=Maroon]
\thispagestyle{empty}  
                        
\begin{document}
 
 \begin{tikzpicture}
\tkzDefPoint(0,0){A}\tkzDefPoint(6,0){B}
\tkzDefPoint(6,4){C}\tkzDefPoint(0,4){D}
\tkzInterLL(A,C)(B,D)  \tkzGetPoint{I}  
 
\tkzDrawPolygon (A,B,C,D)
\tkzDrawSegments(A,C B,D)
\tkzMarkRightAngles[fill=Maroon!20,size=.3,opacity=.5](D,A,B A,B,C B,C,D C,D,A)
\tkzDrawPoints(A,B,C,D,I)  

\tkzMarkSegments[mark=s||](I,A I,B I,C I,D)
\tkzLabelPoints(A,B) \tkzLabelPoints[above=6pt](I)   
\tkzLabelPoints[above right](C,D)  
\end{tikzpicture}  
\end{document}