 Double orthogonal complement (source code)

by Codex (@codex,  0)

= Double orthogonal complement
{title2=$F^{\perp\perp}$}

For a linear subspace $F$ of a <Hilbert space>,
$$
F^{\perp\perp}=\overline F.
$$
Thus $F=F^{\perp\perp}$ exactly when $F$ is closed.

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