ANNALS OF FUNCTIONAL ANALYSIS, cilt.6, ss.221-226, 2015 (SCI İndekslerine Giren Dergi)
The distance from the nonconstant function phi in L-infinity(T) to the set F-const of all constant functions is estimated in terms of Hankel operators on the Hardy space H-2(D) over the unit disk D = {z is an element of C : \z\ < 1}. We give a sufficient condition ensuring the equality dist(phi, F-const) = ||phi||(L infinity). Some other dist-formulas are also discussed.