Abstract
An upper bound for the best approximation of periodic summable functions of two variables in the metric of L is obtained in terms of Fourier coefficients. Functions that can be represented by trigonometric series with coefficients satisfying a two-dimensional analog of the Boas–Telyakovskii conditions are considered.
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Kononovych, T.O. Estimate for the Best Approximation of Summable Functions of Two Variables in Terms of Fourier Coefficients. Ukrainian Mathematical Journal 56, 62–85 (2004). https://doi.org/10.1023/B:UKMA.0000031703.58056.76
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DOI: https://doi.org/10.1023/B:UKMA.0000031703.58056.76