ON THE DERIVATIVE OF ITERATIONS OF THE MINKOWSKI QUESTION MARK FUNCTION AT SPECIAL POINTS

摘要

For the Minkowski question mark function ?(x) we consider derivative of the function f(n)(x) = ?)?(...?(x))).}n times Apart from obvious cases (rational numbers for example) it is non-trivial to find explicit examples of numbers x for which f'(n)(x) = 0. In this paper we present a set of irrational numbers, such that for every element x(0) of this set and for any n is an element of Z(+) one has f'(n)(x(0)) = 0.