\documentclass[12pt,a4paper]{article}
\usepackage{french}

\topmargin=-1.5cm
\textwidth=17cm
\textheight=25cm
\oddsidemargin=-0cm

\newtheorem{prop}{Proposition}[section]
%\newtheorem{defi}{D\'efinition}[chapter]
\newtheorem{propr}{Propri\'et\'e}[section]
\newtheorem{lem}[prop]{Lemme}
\newtheorem{corp}[prop]{Corollaire}
\newtheorem{thm}{Th\'eor\`eme}[section]
\newtheorem{cort}[thm]{Corollaire}
%\newtheorem{theo}{Th\'eor\`eme}[chapter]
%\newtheorem{lemm}[theo]{Lemme}
%\newtheorem{cort}[theo]{Corollaire}
%\newtheorem{rem}{Remarque}[chapter]
%\newtheorem{rems}[rem]{Remarques}

\newcommand{\Z}{\tilde{Z}}
\newcommand{\Y}{\tilde{Y}}
\newcommand{\X}{\tilde{X}}
\newcommand{\U}{\tilde{U}}
\newcommand{\num}{n$^{\mbox{{\footnotesize o}}}$}
\newcommand{\noi}{\noindent}
\newcommand{\und}{\underline}
\newcommand{\ra}{\rightarrow}
\newcommand{\ral}{\longrightarrow}
\newcommand{\lar}{\leftarrow}
\newcommand{\Lra}{\Leftrightarrow}
\newcommand{\DP}{\displaystyle}
\newcommand{\al}{\alpha}
\newcommand{\be}{\beta}
\newcommand{\de}{\delta}
\newcommand{\De}{\Delta}
\newcommand{\ga}{\gamma}
\newcommand{\Ga}{\Gamma}
\newcommand{\ep}{\epsilon}
\newcommand{\va}{\varphi}
\newcommand{\la}{\lambda}
\newcommand{\La}{\Lambda}
\newcommand{\te}{\theta}
\newcommand{\Te}{\Theta}
\newcommand{\om}{\omega}
\newcommand{\Om}{\Omega}
\newcommand{\si}{\sigma} 
\newcommand{\ot}{\otimes}
\newcommand{\ti}{\times}
\newcommand{\var}{\varepsilon}
                                                                                                                 
\newcommand{\limps}{\lim_{n\to\infty}\mbox{p.s. }}

\newenvironment{preuve}{{\bf Preuve:}}{\par}
\newenvironment{note}{\em \noindent Note~:}{\par}
\newenvironment{rem}{{\bf Remarque:}}{\par}

%E \`a l'envers barr\'e (nonexists)
\def\eb{\hbox{$\exists$\hskip -7.6pt$\not$}}

\def \ind{\hbox{1\hskip -3.2pt I}}
\def \P{\hbox{\rm I}\!\hbox{\rm P}}
\def \E{\hbox{I}\!\hbox{E}}
\def \N{\hbox{I}\!\hbox{N}}
\def \Ent{\hbox{\rm Ent}}

\def \R{\hbox{I}\!\hbox{R}}
\def\cit{\hbox{\it l\hskip -5.5pt C\/}}
\def\zit{\hbox{\it Z\hskip -4pt Z}}
\def\zitbf{\hbox{\it \bf Z\hskip -7pt Z}}
\def\qit{\hbox{\it l\hskip -5,5pt Q}}
\def\tit{\hbox{\it I\hskip -5pt T}}


% D\'efinition : "cadre". Pour encadrer une formule math\'ematique X :
% Dans le texte, tapez $\cadre{ X }$ ; Hors texte, tapez $$ idem $$ ;
% Pour encadrer du texte, tapez $\cadre{\hbox{ texte }}$ ou $$ idem $$.
\def\cadre#1{\vcenter
{\hrule\hbox{\vrule
\kern3pt\vbox{\vskip3pt\hbox{$\displaystyle #1$}\vskip3pt}\kern3pt
\vrule}\hrule}}
 
\def\build#1_#2^#3{\mathrel{\mathop{\kern 0pt#1}\limits_{#2}^{#3}}}


\begin{document}