The generalized Cantor function Ѳϒ has a derivative equal to 1/(1 — γ) at almost every point in the set Cγ. This was established by Darst [1] who then posed the problem of characterizing those points ...

Let X be a normed linear space, Un an n-dimensional Chebyshev subspace of X. For f ∈ X denote by p(f) ∈ Un its best approximation in Un. The problem of strong unicity consists in estimating how fast ...