Jackson's type estimate of nearly coconvex approximation

German Dzyubenko

Suppose that a continuous on the real axis $2\pi$-periodic function $f$ changes its convexity at $2s,s\in \mathbb{N},$ points $y_i$ on each period: $-\pi \le y_{2s}<y_{2s-1}<...<y_1<\pi ,$ an…