кусочно-линейные функции

Approximation Properties of Dicrete Fourier Sums for Some Piecewise Linear Functions

Authors: Akniev G. G.

Let N be a natural number greater than 1. We select N uniformly distributed points t_k = 2πk/N (0 < k < N − 1) on [0,2\pi]. Denote by  L_ n,N (f) = L _n,N (f,x)1 < n < ⌊N/2⌋  the trigonometric polynomial of order n possessing the least quadratic deviation from f with respect to the system tk{k=0}^{N-1}. In other words, the greatest lower bound of the sums on the set of trigonometric polynomials Tn of order n is attained by L_n,N (f). In the present article the problem of function approximation by the polynomials L_n,N (f,x)  is considered.

Gluing Rule for Bernstein Polynomials on the Symmetric Interval

Authors: Tikhonov I. V., Sherstyukov V. B., Petrosova M. A.

We study special laws that arise in a sequence of the Bernstein polynomials on a symmetric interval. In particular, we set the exact rule of regular pairwise coincidence (gluing rule) which is acting for the Bernstein polynomials of a piecewise linear generating function with rational abscissas of break points. The accuracy of this rule for convex piecewise linear generating functions is shown. The possibility of “random” gluing for the Bernstein polynomials in a non-convex case is noted. We give also some examples and
illustrations.