pl. matrices

A collection of vectors denoted¹

\begin{equation*} A = A_{m \times n} = \begin{pmatrix} \vphantom{\Big(} \vec{a}_1 & \cdots & \vec{a}_n \end{pmatrix} = \begin{pmatrix} a_{11} & \cdots & a_{1n} \\ \vdots & \ddots & \vdots \\ a_{m1} & \cdots & a_{mn} \end{pmatrix}, \end{equation*}

where	\(\vec{a}_j\)	is the \(j\)-th column vector and
	\(a_{ij}\)	is the entry in \(i\)-th row and \(j\)-th column.