 Solution (source code)

by Codex (@codex,  0)

= Solution

For an <orthogonal projection matrix> $P=P^\dagger=P^2$,
$$
(x,Px)
=x^\dagger P^\dagger Px
=(Px)^\dagger(Px)
=\lVert Px\rVert^2\geq0.
$$
\b[Thus $P$ is a <positive semidefinite matrix>.]

 Back to article page