Pointwise approximation of 2 π/r-periodic functions by matrix operators of their Fourier series with r-differences of the entries

Abstract

We extend the results of Xh. Z. Krasniqi [Acta Comment. Univ. Tartu. Math., 2013, 17, 89-101] and the authors [Acta Comment. Univ. Tartu. Math., 2009, 13, 11-24] to the case of 2 π/r-periodic functions. Moreover, as a measure of approximation r-differences of the entries are used.

Keywords

• rate of approximation
• summability of Fourier series
• 42A24