**5.1.1. Matrix terminology & notation**

\(n\times m\) matrix has \(n\) rows and \(m\) columns, \(A_{i,j}\) is entry in row \(i\) and column \(j\),

\(A'=A^T\) is the transpose. \(|A| = \det A\) is the determinant, \(I_n\) is the identity matrix, \(0_{n\times m}\) is the zero matrix,

\(\mathrm{tr}(A)\) is the trace, \(A^{-1}\) is the inverse