APPROXIMATION BY CESÀRO MEANS OF NEGATIVE ORDER OF DOUBLE WALSH-KACZMARZ-FOURIER SERIES

Abstract

In this article we investigate the rate of the approximation by Cesàro means of the quadratical partial sums of double Walsh-Kaczmarz-Fourier series of a function in the Lebesgue space over the Walsh group. The approximation properties of Cesàro means of negative order of one- and two-dimensional Walsh-Fourier series was discussed earlier by Goginava.