136 名前:fν is discontinuous (and consequently not differentiable) at the rationals, and continuous at the irrationals. With respect the differentiability, we have: (a) For every irrational number x with bounded elements in its continued fraction expansion, fν is differentiable at x. (b) There exist infinitely many irrational numbers x such that fν is not differentiable at x. Moreover, the sets of numbers that fulfill (a) and (b) are both of them un-countable. (引用終り)