f(x) = x^αsin(1/x^β), x ≠ 0 f(x) = 0, x = 0 f'(0) = lim [x^αsin(1/x^β) - 0]/(x-0) = lim x^(α-1)sin(1/x^β) α > 1 时,f'(0) = 0. f'(x) = αx^(α-1)sin(1/x^β) - βx^(α-β-1)cos(1/x^β), α > 1 且 α-β-1 > 0 时,即 α > β + 1 时 f'(x) 在 x。