Chebyshev Approximation by A + B* log (1 + CX). II
Charles B. Dunham · IMA Journal of Applied Mathematics · 1972
The set of all first degree polynomials must be added to the set of approximations of the form a + b log (1 + cx) in order that a best Chebyshev approximation exist to all continuous functions on [0, α]. Best approximations in this augmented family of approximations are characterized by alternation of their error curve and are unique. The Chebyshev operator is continuous at f if f is an approximant or f has a non-constant best approximation.