Matrices et LaTeX

\RequirePackage{pgf, tikz, pgfplots}
\usetikzlibrary{arrows, shapes, calc, patterns, matrix, decorations.pathreplacing}

\newcommand{\tikzmarkbase}[2]{\tikz[overlay, remember picture] \node[inner sep=0pt, outer sep=5pt, anchor=base] (#1) {#2};}
\newcommand{\tikzmarktop}[2]{\tikz[overlay, remember picture] \node[inner sep=0pt, outer sep=2pt, anchor=base] (#1) {#2};}
\newcommand{\tikzmarkright}[2]{\tikz[overlay, remember picture] \node[inner sep=0pt, outer sep=2pt, anchor=base] (#1) {#2};}

%---

\begin{document}

%---

\begin{figure}
\[\left(
	\begin{array}{cccccc}
		& \multicolumn{1}{|c}{\tikzmarktop{pivot1}{1}} &   & * &   & \tikzmarkright{acco1h}{$*$} \\ \cline{2-2}
		& & \multicolumn{1}{|c}{\tikzmarktop{pivot2}{1}} & \tikzmarkbase{second1}{$*$} &   & * \\ \cline{3-4}
		& & & & \multicolumn{1}{|c}{\tikzmarktop{pivot3}{1}} & \tikzmarkbase{second2}{\tikzmarkright{acco1b}{$*$}} \\ \cline{5-6}
		&&&&&\tikzmarkright{acco2h}{\null} 
		\\
		&&&&&\tikzmarkright{acco2b}{\null} 
	\end{array}
\right)\]
\tikz[overlay,remember picture,>=stealth] {
  %
  \node[shift={(0,2em)}] (top1) at (pivot1) {};
  \draw[->] (top1) -- (pivot1);
  \node (top2) at (pivot2|-top1) {};
  \draw[->] (top2) -- (pivot2);
  \node (top3) at (pivot3|-top1) {};
  \draw[->] (top3) -- (pivot3);
  %
  \draw ($(top1)!0.5!(top3)$) node {\scriptsize inconnues principales};
  %
  \node[shift={(0,-5em)}] (base1) at (second1) {};
  \draw[->] (base1) -- (second1);
  \node (base2) at (second2|-base1) {};
  \draw[->] (base2) -- (second2);
  %
  \node (midbase) at ($(base1)!0.5!(base2)$) {};
  \node[shift={(0,-.75em)}] (midbasebas) at (midbase) {};
  \draw (midbase) node {\scriptsize inconnues secondaires,};
  \draw (midbasebas) node {\scriptsize ou paramètres};
  %
  \node[shift={(2em,1.5ex)}] (debacc1) at (acco1h) {};
  \node[shift={(2em,-1.5ex)}] (finacc1) at (acco1b) {};
  \draw [decorate,decoration={brace,amplitude=.25em},shift={(.25em,0)}] (debacc1) -- (finacc1);
  \node[ right] (midacc1) at ($(debacc1)!0.5!(finacc1)$) {\scriptsize\ équations principales};
  %
  \node[shift={(2em,1.5ex)}] (debacc2) at (acco2h) {};
  \node[shift={(2em,-1.5ex)}] (finacc2) at (acco2b) {};
  \draw [decorate,decoration={brace,amplitude=.25em},shift={(.25em,0)}] (debacc2) -- (finacc2);
  \node[ right] (midacc2) at ($(debacc2)!0.5!(finacc2)$) {\scriptsize\ équations secondaires};
}
\end{figure}