DEGREE OF COPOSITIVE POLYNOMIAL APPROXIMATION

摘要

Denoteby n（f） the degree of copositive approximation to f（x） by polynomials of degree≤n. For function f（x） ∈ Ck[-1, 1] which alternates in sign finitely many timesin [-1, 1], the author obtains the following Jackson type estimatesn（f）≤Cn-kw(fk, 1/n)foa any positive integer k.