(a) Let $S$ be the subspace of $\mathcal{M}_{2 \times 2}$ consisting of all symmetric $2 \times 2$ matrices. Show that $S$ is spanned by the matrices $\left(\begin{array}{ll}1 & 0 \\ 0 & 0\end{array}\right),\left(\begin{array}{ll}0 & 0 \\ 0 & 1\end{array}\right)$, and $\left(\begin{array}{ll}0 & 1 \\ 1 & 0\end{array}\right)$.
(b) Find a spanning set of the space of symmetric $3 \times 3$ matrices.