題組內容

二、(50%) (所有題目請敘述計算過程，無計算過程不給分)
1. Let $A = \begin{bmatrix} 2 & 1 & -1 \\ 1 & 2 & 1 \\ -1 & 1 & 2 \end{bmatrix}$

(c) Orthogonally diagonalize the matrix $ A $. (You need to find out an orthogonal matrix $ P $ and a diagonal matrix $ D $ such that $ P^T AP = D $.) (10%)