% !TeX TXS-program:compile = txs:///pdflatex

\documentclass[margin=5mm]{standalone}
\usepackage[nonpgfplots]{tkz-grapheur}

\begin{document}

\begin{GraphiqueTikz}[x=1.1cm,y=2.17cm,Xmin=-1,Xmax=4.5,Ymin=-1,Ymax=1.5]
	\def\valx{2.1}
	\TracerAxesGrilles[Grille=false]{}{}
	\DefinirCourbe[Nom=cf,Debut=0.1,Trace,Couleur=red]{ln(x)}
	\draw[pfltraitantec] (\valx,0) node[below] {$x$} -- (\valx,{ln(\valx)}) node[above left] {$M$} ;
	\MarquerPts*[Style=+]{(\valx,{ln(\valx)})}
	\draw[line width=0.9pt] (\valx,{ln(\valx)}) -- (0,0) node[below left] {$O$};
	\PlacerTexte[Couleur=red,Position=above left]{(3.25,{ln(3.25)})}{$\mathcal{C}_{g}$}
\end{GraphiqueTikz}

\end{document}