A square matrix A of order n is said to be symmetric if \(a_{i,\space j}\) = \(a_{j,\space i}\) for \(i,\space j\) ∈ {1, 2, 3, 4, …, n}.
In a symmetric matrix, the main diagonal is a line of symmetry for the elements located on either side of the diagonal.
Example
The matrices A = \(\begin{pmatrix}–3 & 5\\5 & – 3\end{pmatrix}\) and B = \(\begin{pmatrix}–3 & 5 & 6\\5 & 0 & 2\\6 & 2 & –1\end{pmatrix}\) are symmetric matrices.