Why is $(V^\perp)^\perp=\overline{V}$ when $V$ is a subspace of a Hilbert space $H$? I googled about this but only $V$ as a subspace of finite vector space. Any reference or proof or idea are welcome.
2026-04-07 05:10:28.1775538628
Is $(V^\perp)^\perp=\overline{V}$ when $V$ is a subspace of a Hilbert space $H$?
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