Best Trigonometric Approximation, Fractional Order Derivatives and Lipschitz Classes

Butzer, P. L. ; Dyckhoff, H. ; Görlich, E. ; Stens, R. L.

Canadian journal of mathematics, Tome 29 (1977) no. 4, pp. 781-793

Résumé

Let C 2π denote the space of 2π-periodic continuous functions and πn the set of trigonometric polynomials of degree ≦ n, where n ε P = {0, 1, ... } . Given θ > 0, the well-known theorem of Stečkin and its converse state that the best approximation of an ƒ ε C 2π with respect to the max-norm satisfies

Détail

DOI : 10.4153/CJM-1977-081-6

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