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JOURNALS // Izvestiya of Saratov University. Mathematics. Mechanics. Informatics // Archive

Izv. Saratov Univ. Math. Mech. Inform., 2015 Volume 15, Issue 4, Pages 418–422 (Mi isu609)

This article is cited in 1 paper

Mathematics

Interpolation of continuous in ordered $H$-variation functions

V. V. Novikov

Engels Technological Institute, State Technical University of Saratov, 17, pl. Svobody, 413100, Engels, Saratov region, Russia

Abstract: In 1972 D. Vaterman introduced a class of functions of $\Lambda$-bounded variation (in particular, a harmonic variation or an $H$-variation). Later he introduced also the class of functions of ordered $\Lambda$-bounded variation and the class of continuous in $\Lambda$-variation functions. These classes have been used by many authors in studies on the convergence and summability of the Fourier series. This paper investigates the behavior of the Lagrange interpolation of continuous in ordered $H$-variation functions. We prove a result: if $f\in C_{2\pi}$ is continuous in ordered harmonic variation on $[-\pi,\pi]$, then the Lagrange trigonometric polynomials $\{L_n(f,x)\}$ based on equidistant nodes converge to $f$ uniformly on $\mathbb{R}$.

Key words: generalized variation, ordered harmonic variation, Lagrange interpolation.

UDC: 517.51

DOI: 10.18500/1816-9791-2015-15-4-418-422



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