Jackson's inequality
In approximation theory , Jackson's inequality is an inequality bounding the value of function's best approximation by algebraic or trigonometric polynomials in terms of the modulus of continuity or modulus of smoothness of the function or of its derivatives . 
<triplet> Jackson's inequality <subj> approximation theory <obj> facet of <triplet> trigonometric polynomials <subj> approximation theory <obj> facet of <triplet> modulus of continuity <subj> approximation theory <obj> facet of <triplet> modulus of smoothness <subj> approximation theory <obj> facet of