fundamental command

math command

12.矩阵

\begin{Bmatrix}
1 & 2 & 3 & \cdots & 4 \\\\
5 & 6 & 7 & \cdots & 8 \\\\
\vdots&\vdots&\vdots&\ddots&\vdots\\\\
9&10&11&\cdots&12
\end{Bmatrix}
\tag{1}

\begin{bmatrix}
1 & 2 & 3 & \cdots & 4 \\\\
5 & 6 & 7 & \cdots & 8
\end{bmatrix}
\tag{2}

\begin{matrix}
1 & 2 & 3 & \cdots & 4 \\\\
5 & 6 & 7 & \cdots & 8
\end{matrix}
\tag{3}