Degree of approximation by means of hexagonal Fourier series

Let f be a continuous function which is periodic with respect to the hexagon lattice, and let A be a lower triangular infinite matrix of nonnegative real numbers with nonincreasing rows. The degree of approximation of the function f by matrix means T A n f of its hexagonal Fourier series is estimated in terms of the modulus of continuity of f.

Keywords:

Hexagonal domain, hexagonal Fourier series, Hölder class matrix mean,

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