KnowraBessel's inequalityLinked fromLinked fromThe 6 pages that link to Bessel's inequality, each with the reason it gives.All 6Broader topic 1Related 2Compared with 3Hölder's inequalityRelated: It follows by applying Cauchy–Schwarz-related norm reasoning in inner-product spaces.Orthonormal basisRelated: It bounds coefficient sums even before completeness guarantees equality.Parseval's identityCompared with: It gives the bound that becomes equality when the Fourier system is complete.Parseval's theoremCompared with: It becomes equality under completeness, the condition behind Parseval’s identity.Friedrich Wilhelm BesselBroader topic: This mathematical result carries Bessel’s name and extends beyond his astronomical work.Riesz's lemmaCompared with: Unlike Riesz's lemma, it concerns orthogonal projections and coefficient bounds in inner-product spaces.