Certain inequalities in various metrics for trigonometric polynomials and their derivatives
Matematičeskie zametki, Tome 18 (1975) no. 4, pp. 489-498
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We establish for $0
the analog of the Bernstein–Zygmund inequality for the derivative of a trigonometric polynomial $$ \int_{-\pi}^\pi|t_n'(x)|^pdx\leqslant c_pn^p\int_{-\pi}^\pi|t_n(x)|^pdx. $$ We prove weighted inequalities, exact in the sense of order, for trigonometric polynomials and their derivatives in various integral metrics with exponents $0 , $q\leqslant\infty$.