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

Izv. Saratov Univ. Math. Mech. Inform., 2017 Volume 17, Issue 4, Pages 394–401 (Mi isu733)

Scientific Part
Mathematics

Adjustment of functions and Lagrange interpolation based on the nodes close to the Legendre nodes

V. V. Novikov

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

Abstract: It is well known that the Lagrange interpolation of a continuous function 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 arbitrarily small measure such that its Fourier series will be uniformly convergent. The question arises: does the class of continuous functions have a similar property with respect to any interpolation process? In the present paper we prove that there exists a matrix of nodes $\mathfrak{M}_\gamma$ arbitrarily close to the Legendre matrix with the following property: any function $f\in{C[-1,1]}$ can be adjusted in a set of arbitrarily small measure such that the 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, Legendre orthogonal polynomials, adjustment of functions.

UDC: 517.51

DOI: 10.18500/1816-9791-2017-17-4-394-401



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