Hi,
If I compile the following code, the result is not the one expected.

\usemodule[tikz]
\usetikzlibrary[matrix,decorations.pathreplacing, calc, positioning,fit]
\starttext

\starttikzpicture[>=stealth,thick,baseline,
every right delimiter/.append style={name=rd},
]
\matrix [matrix of math nodes,
    left delimiter=(,
    right delimiter=),
    ](A){
a_{1,1} & a_{1,2} & \dots  & a_{1,j} & \dots & a_{1,n}\\
a_{2,1} & a_{2,2} & \dots  & a_{2,j} & \dots & a_{2,n}\\
\vdots  & \vdots  &  & \vdots  &  & \vdots\\
a_{i,1} & a_{i,2} & \dots  & a_{i,j} & \dots & a_{i,n}\\
\vdots  & \vdots  &  & \vdots  &  & \vdots\\
a_{n,1} & a_{n,2} & \dots  & a_{n,j} & \dots & a_{n,n}\\
};

\draw[<-] (rd)--++(0:6mm) node[right]{$i$-ième colonne};
\draw[<-] (A.south-|A-1-4.center) --++(-90:6mm) node[below]{$j$-ième
colonne};

\stoptikzpicture
\stoptext

Thank you
Fabrice