Ciro Santilli
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# Riesz-Fischer theorem | 🗖 nosplit | ↑ parent "Lebesgue integral of is complete but Riemann isn't" | 56, 4, 287

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A measurable function defined on a closed interval is square integrable (and therefore in ) if and only if Fourier series converges in norm the function: $$limN→∞​∥SN​f−f∥2​=0 (33)$$
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