(sin(ln2/2)+sin(ln3/3)+...+sin(lnn/n))^(1/n)的极限

来源:学生作业帮助网 编辑:六六作业网 时间:2024/11/23 16:00:08
(sin(ln2/2)+sin(ln3/3)+...+sin(lnn/n))^(1/n)的极限(sin(ln2/2)+sin(ln3/3)+...+sin(lnn/n))^(1/n)的极限(sin(l

(sin(ln2/2)+sin(ln3/3)+...+sin(lnn/n))^(1/n)的极限
(sin(ln2/2)+sin(ln3/3)+...+sin(lnn/n))^(1/n)的极限

(sin(ln2/2)+sin(ln3/3)+...+sin(lnn/n))^(1/n)的极限
sin(lnk/k)

  记
   f(x) = lnx/x,

   f'(x) = (1-lnx)/(x^2) < 0,x>e,
得知 f(x) 当 x>e 时单调下降,取
   a = max{sin(ln2/2),sin(ln3/3)},
则 0   a^(1/n) < [sin(ln2/2)+sin(ln3/3)+...+sin(lnn...

全部展开

  记
   f(x) = lnx/x,

   f'(x) = (1-lnx)/(x^2) < 0,x>e,
得知 f(x) 当 x>e 时单调下降,取
   a = max{sin(ln2/2),sin(ln3/3)},
则 0   a^(1/n) < [sin(ln2/2)+sin(ln3/3)+...+sin(lnn/n)]^(1/n) < (n*a)^(1/n)

   lim(n→inf.)a^(1/n) = 1,
   lim(n→inf.)(n*a)^(1/n) = lim(n→inf.)n^(1/n)*lim(n→inf.)a^(1/n) = 1*1 = 1,
据夹逼定理,得知原极限为 1。

收起