Denotebyn（f）thedegreeofcopositiveapproximationtof（x）bypolynomialsofdegree≤n.Forfunctionf（x）∈Ck[-1,1]whichalternatesinsignfinitelymanytimesin[-1,1],theauthorobtainsthefollowingJacksontypeestimatesn（f）≤Cn-kw(fk,1/n)foaanypositiveintegerk.
数学年刊：B辑英文版
1989年3期
