Authors:K. Kopotun, D. Leviatan, and I. A. Shevchuk
The paper deals with approximation of a continuous function, on a finite interval, which changes convexity finitely many times,
by algebraic polynomials which are coconvex with it. We give final answers to open questions concerning the validity of Jackson
type estimates involving the weighted Ditzian-Totik moduli of smoothness.
We investigate the approximation behavior of the so-called Jackson interpolation operator. We will also study the K-functional deduced from this operator. As a result we obtain the asymptotic expression of this K-functional.