# [Tex/LaTex] Upper triangular matrix with big zero in lower triangular

math-modematrices

I can represent an upper trapezoidal matrix say as shown below. I would like to replace all those zeros with a single big zero that spans across the low triangle rows and columns, and maybe also add a delimiter along the diagonal that clearly shows it is an upper diagonal matrix. How can I do that?

\newcommand\x{\XSolid}
%\newcommand\x{\ding{53}}
\begin{equation}
\left(
\begin{array}{*5{c}}
\x & \x & \x & \x & \x \\
0 & \x & \x & \x & \x \\
0 &  0 & \x & \x & \x \\
0 &  0 &  0 & \x & \x \\
0 &  0 &  0 &  0 & \x \\
\end{array}\right)
\end{equation}


Separate question … why the \x command I define outputs # rather than the intended cross symbol? It outputs the same symbol # no matter if I use \XSolid or \ding{53}

UPDATE: taking the answer as input, I ended doing this:

\newcommand\x{\times}
\newcommand\bigzero{\makebox(0,0){\text{\huge0}}}
\newcommand*{\bord}{\multicolumn{1}{c|}{}}
\begin{equation}
\left(
\begin{array}{ccccc}
\x    & \x       & \x    & \x    & \x \\ \cline{1-1}
\bord & \x       & \x    & \x    & \x \\ \cline{2-2}
& \bord    & \x    & \x    & \x \\ \cline{3-3}
& \bigzero & \bord & \x    & \x \\ \cline{4-4}
&          &       & \bord & \x \\ \cline{5-5}
\end{array}\right)
\end{equation}


which produces this: \documentclass[]{article}
\usepackage{mathtools}
\begin{document}

$\left( \begin{array}{ccccc} 1 \\ & 1 & & \text{\huge0}\\ & & 1 \\ & \text{\huge0} & & 1 \\ & & & & 1 \end{array} \right)$

\end{document} or \makebox(0,0){\text{\huge0}} if you want to have the same line spacing.