@article{Vakarchuk_Vakarchuk_2022, title={$K$-functionals and extreme problems of the theory of approximation of the classes of analytic functions in a circle. II}, volume={74}, url={https://umj.imath.kiev.ua/index.php/umj/article/view/6981}, DOI={10.37863/umzh.v74i7.6981}, abstractNote={<p>UDC 517.5</p> <p>The exact values of the Kolmogorov, Bernstein, and trigonometric $n$-widths of the classes defined by using the Hadamard compositions, generalized $K$-functionals, and majorants are obtained in the Hardy, Bergman, and Gvaradze Banach spaces. <br>The exact values of the upper boundaries of the moduli of Fourier coefficients were also found in the indicated classes of functions.</p>}, number={7}, journal={Ukrainsâ€™kyi Matematychnyi Zhurnal}, author={Vakarchuk, S. B. and Vakarchuk, M. B.}, year={2022}, month={Aug.}, pages={921 - 929} }