Stechkin's problem for functions of a self-adjoint operator in a Hilbert space, Taikov-type inequalities and their applications

Vladyslav Babenko, Yuliya Babenko, Nadiia Kriachko

In this paper we solve the problem of approximating functionals $(\phi (A)x,f)$ (where $\phi (A)$ is some function of self-adjoint operator $A$) on the class of elements of a Hilbert spac…