我怎样才能写出这样的块矩阵？

Question

有人可以帮我写这个矩阵吗？

Answer 1

\documentclass{article}

\usepackage{amsmath}

\begin{document}

Thus the matrix representation~$\mathcal{L}$ under the basis is
\[
  \begin{pmatrix}
    A &   &        & 0 \\
      & A &        &   \\
      &   & \ddots &   \\
    0 &   &        & A
  \end{pmatrix}
\]
The desired result follows immediately.

\end{document}

Answer 2

在 Plain TeX 中，你的文档如下所示：

Thus the matrix representation~$\cal L$ under the basis is
$$
  \pmatrix{ A &   &        & 0 \cr
              & A &        &   \cr
              &   & \ddots &   \cr
            0 &   &        & A }
$$
The desired result follows immediately.
\bye