Abstract
We obtain new inverse theorems on the approximation of periodic functions f(·) that establish conditions for the existence of their (ψ, β)-derivatives. These theorems also guarantee a certain smoothness of these derivatives.
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Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 47, No. 9, pp. 1266–1273, September, 1995.
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Stepanets, A.I. Inverse theorems on approximation of periodic functions. Ukr Math J 47, 1441–1448 (1995). https://doi.org/10.1007/BF01057519
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DOI: https://doi.org/10.1007/BF01057519