On One Counterexample in Convex Approximation

• Date: 2000
• Main Authors: Yushchenko, L. P., Ющенко, Л. П.
• Format: Article
• Language: Ukrainian; English
• Published: Institute of Mathematics, NAS of Ukraine 2000
• Online Access: https://umj.imath.kiev.ua/index.php/umj/article/view/4576
• Journal Title: Ukrains’kyi Matematychnyi Zhurnal

We prove the existence of a function fcontinuous and convex on [−1, 1] and such that, for any sequence {p n} n= 1 ∞of algebraic polynomials p nof degree ≤ nconvex on [−1, 1], the following relation is true: \(\begin{array}{*{20}c} {\lim \sup } \\ {n \to \infty } \\ \end{array} \begin{array}{*{20}c...