Sign-Preserving Approximation of Periodic Functions

• Date: 2003
• Main Authors: Pleshakov, M. G., Popov, P. A., Плешаков, М. Г., Попов, П. А.
• Format: Article
• Language: Russian; English
• Published: Institute of Mathematics, NAS of Ukraine 2003
• Online Access: https://umj.imath.kiev.ua/index.php/umj/article/view/3983
• Journal Title: Ukrains’kyi Matematychnyi Zhurnal

We prove the Jackson theorem for a zero-preserving approximation of periodic functions (i.e., in the case where the approximating polynomial has the same zeros y i) and for a sign-preserving approximation [i.e., in the case where the approximating polynomial is of the same sign as a function f on ea...