\documentclass[10pt]{article}
\usepackage{a4}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{latexsym}
\usepackage[french]{babel}
\usepackage{epsfig}

\renewcommand{\baselinestretch}{1}
\newcommand{\bm}[1]{\mbox{\boldmath $ #1 $ }}
\newcommand{\model}[1]{\mbox{\boldmath$#1$\unboldmath}}
\newcommand{\emmodel}[1]{\mbox{\em {\bf #1}}}
\newcommand{\vs}{\vspace{1cm}}
\newcommand{\hs}{\hspace{1cm}}
\newcommand{\pp}{\vspace{6 mm}}
\newcommand{\ov}{\overline}
\newcommand{\N}{\mathbb N}
\newcommand{\Z}{\mathbb Z}
\newcommand{\Q}{\mathbb Q}
\newcommand{\R}{\mathbb R}
\newcommand{\C}{\mathbb C}

\newtheorem{exemple}{Exemple}[section]
\newtheorem{remarque}{Remarque}[section]
\newtheorem{notation}{Notation} % [section]

\newcommand{\entourer}[1]{\rlap{\raisebox{-3pt}{\Huge$\bigcirc$}}\makebox[24pt][c]{#1}}