For double trigonometric Fourier series, Móricz and Rhoades studied the rate of uniform approximation by Nörlund means of the rectangular partial sums of double Fourier series of a function belonging to the class Lipα (0 < α 1) [12] and the class of continuous functions [13], on the two-dimensional torus. As a special case, they obtained the rate of uniform approximation by double Cesàro means....

• Asymptotics of the Lebesgue constant for Lagrange interpolation based on Lissajous-Chebyshev node points. partial sums Fourier series generated by anisotropically dilated rhombus. Formula Dirichlet kernel with frequencies in In this paper asymptotic formulas are given constants three special approximation processes related to ? 1 -partial series. particular, we consider polynomials points, rh...