Define the shift map $S: \mathbb{C}^n \rightarrow \mathbb{C}^n$ by $S\left(v_1, v_2, \ldots, v_{n-1}, v_n\right)^T=\left(v_2, v_3, \ldots, v_n, v_1\right)^T$.
(a) Prove that $S$ is a linear map, and write down its matrix representation $A$.
(b) Prove that $A$ is an orthogonal matrix. (c) Prove that the sampled exponential vectors $\omega_0, \ldots, \omega_{n-1}$ defined in (5.102) form an eigenvector basis of $A$. What are the eigenvalues?