Approximation of classes $\overline{\psi}$-differentiated functions by the Fourier sums

Abstract

We consider deviations of Fourier sums on the spaces $C^{\overline{\psi}}_{\infty}$ and estimates of these deviations are expressed by the best approximation $\overline{\psi}$-derivative functions of two variables in the understanding of A.I.Stepanets are obtained. The sequence $\psi_i^{(j)}(k_i),$ $i=1,2,$ $j=1,2,$ are quasiconvex functions.