Let be a quasi-smooth curve in the complex plane C. In this study, a direct theorem of approximation theory in certain subclasses of the functions which have continuous derivatives through order r on a closed curve is proved.
Mathematics Subject Classification
Definitions, Some Auxiliary Results and Main ResultLet be an arbitrary restricted Jordan curve with two-component complements = C = 1 ∪ 2 , (0 ∈ 1 , ∞ ∈ 2 ). Let us consider the functions w = φ i (z), (i = 1, 2), that conformally and univalently map, respectively, i onto i , 1 = {w : |w| < 1}, 2 = {w : |w| > 1} , with norm φ 1 (0) =0, φ 1 (0) > 0, φ 2 (∞) = ∞, lim z→∞ 1 z φ 2 (z) > 0. Let us extend each φ i (z), (i = 1, 2) continuously up to the bound = ∂ 1 = ∂ 2 (generally speaking φ 1 (z) = φ 2 (z) for z ∈ ). We preserve the notation φ i , (i = 1, 2) for the extension. Let z = i (w) be the inverse mapping of w = φ i (z), (i = 1, 2) . LetFor arbitrary natural number n we set1+ (−1) i n (z) := inf ζ 1+ (−1) i n |ζ − z| , ρ1 n (z) := min ρ 1+ (−1) i n (z) , i = 1, 2