We are given a polynomial $P \in \mathbb{C}[X]$ of degree $d$. Deduce from question 3.17 that: $$\|P\|_{\mathbb{D}} = \|P\|_{\partial\mathbb{D}}$$ One may apply question 3.17 to an element $z \in \mathbb{D}$ such that $|P(z)| = \|P\|_{\mathbb{D}}$.
We are given a polynomial $P \in \mathbb{C}[X]$ of degree $d$. Deduce from question 3.17 that:
$$\|P\|_{\mathbb{D}} = \|P\|_{\partial\mathbb{D}}$$
One may apply question 3.17 to an element $z \in \mathbb{D}$ such that $|P(z)| = \|P\|_{\mathbb{D}}$.