Abstract
In the present note we will investigate the problem of the one-sided approximation of functions by n-dimensional subspaces. In particular, we will find the exact value of the best one-sided approximation of the class WrL1 (r=1, 2, ...) of all periodic functions f(x) of period 2π for which f(r−1)(x) (f(0)(x)=f(x)) is absolutely continuous and ∥f(r)∥L1≤1 by periodic spline functions S2nμ (μ = 0, 1, ..., n=1, 2, ...) of period 2π, order μ,and deficiency 1.
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Translated from Matematicheskie Zametki, Vol. 19, No. 1, pp. 11–17, January, 1976.
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Doronin, V.G., Ligun, A.A. Upper bounds for the best one-sided approximation by splines of the classes WrL1 . Mathematical Notes of the Academy of Sciences of the USSR 19, 7–10 (1976). https://doi.org/10.1007/BF01147610
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DOI: https://doi.org/10.1007/BF01147610