Suppose that $\mathbb R^2$ is a Hilbert space. I am having trouble with proving that $span\{(cosx,sinx)\}$ is closed, where x $\in$ $[0,2]$.
This small proof comes from a big proof, which is essential to finish off.
2026-03-26 14:25:21.1774535121
Proving a spanning set is a closed subspace of a Hilbert Space
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