Question
If $U$ is unitary and $Q$ is a real orthogonal matrix, show that $U^{-1}$ is unitary and also II $O$ is unitary. Start from $U^{\mathrm{H}} U=I$ and $Q^{\mathrm{T}} Q=1$.
Step 1
This implies that $U^{-1} = U^H$. Show more…
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