I was reading an alternative orthogonal projector proof.
Let $P$ be an orthogonal projector. Why does $P = P^T P$ imply $P^T = P$ and $P^2 = P$?
2026-03-25 21:45:07.1774475107
Proof on orthogonal projectors
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Because $P^T=(P^TP)^T=P^TP=P$ and thus $P^2=PP=P^TP=P$