A matrix, A ? R<sup>nxn</sup>, such that A = A<sup>T</sup> is called a symmetric matrix. Let A be diagonalizable, i.e., A has an eigen-decomposition, A = VDV<sup>-1</sup>.
In other words, a symmetric matrix has orthogonal eigenvectors, i.e., VV<sup>T</sup> = I, and column-wise we can write
$v_i^T v_j = \begin{cases} 1, & i = j; \\ 0, & i \neq j. \end{cases}$ (1)
(b) Let
$A = \begin{bmatrix} 5 & 4 \\ 4 & 3 \end{bmatrix}$.
Show that its eigenvectors are orthogonal. (Compute the eigenvectors and show that they satisfy Eq. (1)). Plot the eigenvectors and show that they are 90° apart.