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I've a new issues

\setlength{\parindent}{5 em} 
\begin{tabular}{rcll}\label{test}
$\omega \in \lim\limits_n \sup A_jn$ &(\Longleftrightarrow) & $\forall p, \exists n \ge p, 
\text{tel que } \omega \in A_n$ \\
  
 $&\Longleftrightarrow& \omega \text{ appartient à une infinité de } A_n$ \\
  
 &\Longleftrightarrow& $\sum\limits_n \textbf{1}_{A_n}(\omega) = + \infty$ \\
\end{tabular}
4

1 Answer 1

6

You shouldn't be using a tabular environment at all. Instead, do use either an array environment (which uses math mode automatically) or one of multi-row math environments -- such as the alignat environment -- provided by the amsmath package. Either way, you won't be needing to type so many $ tokens.

Here are two array-based solutions -- one uses inline-style math mode, the other display-style math mode -- and one alignat*-based solution. For the case at hand, one might say that the second and third solutions look very much alike. That is, of course, not coincidence. The second array-based solution is, overall, more straightforward to implement than the alignat*-based solution is.

enter image description here

\documentclass{article}
\usepackage[french]{babel}
\usepackage{array}   % for '\newcolumntype' macro
\usepackage{amsmath} % for '\text' macro and 'alignat*' environment

\newcolumntype{C}{>{{}}c<{{}}} % col type for math operators
\newcolumntype{L}{>{\displaystyle}l} 
\newcolumntype{R}{>{\displaystyle}r}
\newcommand\myLongleftrightarrow{\hphantom{(}\mathrel{\Longleftrightarrow}\hphantom{)}}

\begin{document}

\[
\setlength\arraycolsep{0pt} % default value: 5pt
\begin{array}{rCl} % use 'array', not 'tabular'
\omega \in \lim_n \sup A_jn 
  & \mathrel{(\Longleftrightarrow)}
  & \forall p,\ \exists n \ge p \text{ tel que } \omega \in A_n\\
  & \Longleftrightarrow
  & \omega \text{ appartient à une infinité de } A_n \\
  & \Longleftrightarrow  
  & \sum_n \textbf{1}_{A_n}(\omega) = +\infty
\end{array}
\]

\bigskip
\[
\setlength\arraycolsep{0pt}      % default value: 5pt
\renewcommand\arraystretch{1.4}  % default value: 1.0
\begin{array}{RCL}               % use display-style math
\omega \in \smash[b]{\lim_n} \sup A_jn 
  & \mathrel{(\Longleftrightarrow)}
  & \forall p,\ \exists n \ge p \text{ tel que } \omega \in A_n\\
  & \Longleftrightarrow
  & \omega \text{ appartient à une infinité de } A_n \\
  & \Longleftrightarrow  
  & \sum_n \textbf{1}_{A_n}(\omega) = +\infty
\end{array}
\]

\begin{alignat*}{2}
\omega \in \smash[b]{\lim_n} \sup A_jn 
  & \mathrel{(\Longleftrightarrow)}
  &&\forall p,\ \exists n \ge p \text{ tel que } \omega \in A_n\\
  & \myLongleftrightarrow
  &&\omega \text{ appartient à une infinité de } A_n \\
  & \myLongleftrightarrow
  &&\smash[t]{\sum_n} \textbf{1}_{A_n}(\omega) = +\infty
\end{alignat*}

\end{document}
2
  • 1
    Why \mathbin and not \mathrel?
    – egreg
    Dec 17, 2022 at 18:06
  • 1
    @egreg - No good reason. :-) Fixed now.
    – Mico
    Dec 17, 2022 at 19:18

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