
답변1
의 .{pNiceMatrix}
nicematrix
\documentclass[12pt]{article}
\usepackage{nicematrix}
\begin{document}
\[\begin{pNiceMatrix}
X_{11} & X_{12} & \Cdots & X_{1n} \\
X_{21} & \Block{3-3}<\Large>{B} \\
\Vdots \\
X_{1n} \\
\CodeAfter
\SubMatrix[{2-2}{4-4}][xshift=-1ex,extra-height=-1ex]
\end{pNiceMatrix}\]
\end{document}
여러 컴파일이 필요합니다( nicematrix
내부적으로 PGF/Tikz 노드를 사용하기 때문에).
답변2
오직amsmath
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
\begin{bmatrix}
x_{11} & \begin{matrix} x_{12} & \dots & x_{1n} \end{matrix} \\
\begin{matrix} x_{21} \\ \vdots \\ x_{n1} \end{matrix} &
\begin{bmatrix}
\hspace*{-\arraycolsep}
\phantom{x_{11}} & \phantom{x_{11}} & \phantom{x_{11}}
\hspace*{-\arraycolsep}
\\
& \raisebox{-0.2\height}[0pt][0pt]{\LARGE$B$} & \\
& &
\end{bmatrix}
\end{bmatrix}
\]
\end{document}