\documentclass{standalone}

\usepackage{tikz}


\begin{document}
   \begin{tikzpicture}
      \node[anchor=south west] at (0,0)
      {$
         \left(\begin{array}{cccccc}
           a_{11}&a_{12}&\cdots&a_{1j}&\cdots&a_{1n}\\
           a_{21}&a_{22}&\cdots&a_{2j}&\cdots&a_{1n}\\
           \vdots&\vdots&&\vdots&&\vdots\\
           a_{i1}&a_{i2}&\cdots&a_{ij}&\cdots&a_{in}\\
           \vdots&\vdots&&\vdots&&\vdots\\
           a_{m1}&a_{m2}&\cdots&a_{mj}&\cdots&a_{mn}\\
         \end{array}\right)
      $};
      
      \tikzmath{\xxi=3.55;}
      \tikzmath{\yyi=1.425;}
      
      \draw (0.6,\yyi) -- (5.5,\yyi);
      \draw (\xxi,0.1) -- (\xxi,3.1);
   \end{tikzpicture}
\end{document}
