On a~relationship in the theory of Fourier series
Matematičeskie zametki, Tome 15 (1974) no. 5, pp. 679-682
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In this paper we prove the validity of the inequality
$$
\sup\limits_n\int_{-\pi}^\pi\Bigl|\frac{f(0)}2+\sum_{k=1}^nf\bigl(\frac{k\pi}n\bigr)e^{ikt}\Bigr|\,dt\le C\sum_{m=0}^\infty\Bigl|\int_0^\pi f(t)e^{imt}\,dt\Bigr|
$$
for an arbitrary continuous function ($C$ is an absolute constant). An inequality in the opposite sense was obtained by one of us earlier.
@article{MZM_1974_15_5_a2,
author = {\`E. S. Belinskii and R. M. Trigub},
title = {On a~relationship in the theory of {Fourier} series},
journal = {Matemati\v{c}eskie zametki},
pages = {679--682},
publisher = {mathdoc},
volume = {15},
number = {5},
year = {1974},
language = {ru},
url = {http://geodesic.mathdoc.fr/item/MZM_1974_15_5_a2/}
}
È. S. Belinskii; R. M. Trigub. On a~relationship in the theory of Fourier series. Matematičeskie zametki, Tome 15 (1974) no. 5, pp. 679-682. http://geodesic.mathdoc.fr/item/MZM_1974_15_5_a2/