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

Izv. Saratov Univ. Math. Mech. Inform., 2023 Volume 23, Issue 1, Pages 24–35 (Mi isu965)

Scientific Part
Mathematics

Function correction and Lagrange – Jacobi type interpolation

V. V. Novikov

Saratov State University, 83 Astrakhanskaya St., Saratov 410012, Russia

Abstract: It is well-known that the Lagrange interpolation based on the Chebyshev nodes may be divergent everywhere (for arbitrary nodes, almost everywhere), like the Fourier series of a summable function. On the other hand, any measurable almost everywhere finite function can be “adjusted” in a set of an arbitrarily small measure such that its Fourier series will be uniformly convergent. The question arises whether the class of continuous functions has a similar property with respect to any interpolation process. In the present paper, we prove that there exists the matrix of nodes $\mathfrak{M}_\gamma$ arbitrarily close to the Jacoby matrix $\mathfrak{M}^{(\alpha,\beta)}$, $\alpha,\beta>-1$ with the following property: any function $f\in{C[-1,1]}$ can be adjusted in a set of an arbitrarily small measure such that interpolation process of adjusted continuous function $g$ based on the nodes $\mathfrak{M}_\gamma$ will be uniformly convergent to $g$ on $[a,b]\subset(-1,1)$.

Key words: Lagrange interpolation, Jacobi orthogonal polynomials, adjustment of functions.

UDC: 517.51

Received: 31.03.2022
Accepted: 01.10.2022

DOI: 10.18500/1816-9791-2023-23-1-24-35



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