grandes-ecoles 2011 QI.A

grandes-ecoles · France · centrale-maths2__psi Not Maths
Let $\pi$ be the endomorphism of $\mathbb{R}^n$ whose representation in the canonical basis is the matrix $P = I_n - \frac{1}{n}J$, where $J = Z^t Z$ and $Z = \left(\begin{array}{c}1\\ \vdots \\ 1\end{array}\right) \in \mathcal{M}_{n,1}(\mathbb{R})$.
Show that $\pi$ is an orthogonal projector and specify its characteristic elements.
Let $\pi$ be the endomorphism of $\mathbb{R}^n$ whose representation in the canonical basis is the matrix $P = I_n - \frac{1}{n}J$, where $J = Z^t Z$ and $Z = \left(\begin{array}{c}1\\ \vdots \\ 1\end{array}\right) \in \mathcal{M}_{n,1}(\mathbb{R})$.

Show that $\pi$ is an orthogonal projector and specify its characteristic elements.