Projections
Let \(P\in \mathbb {C}^{N\times N}\) be a projection matrix. Prove that \(\ker (P)\perp \operatorname {range}(P)\) if and only if \(P=P^*\). (I.e., you are being asked to justify the definition of an orthogonal projection matrix.)
Question
Spring 2018 • Question 1
Projections
Let \(P\in \mathbb {C}^{N\times N}\) be a projection matrix. Prove that \(\ker (P)\perp \operatorname {range}(P)\) if and only if \(P=P^*\). (I.e., you are being asked to justify the definition of an orthogonal projection matrix.)