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tg(1/nsqrtn)

Sum of series tg(1/nsqrtn)



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The solution

You have entered [src]
  oo            
____            
\   `           
 \       /  ___\
  \      |\/ n |
  /   tan|-----|
 /       \  n  /
/___,           
n = 2           
$$\sum_{n=2}^{\infty} \tan{\left(\frac{\sqrt{n}}{n} \right)}$$
Sum(tan(sqrt(n)/n), (n, 2, oo))
The radius of convergence of the power series
Given number:
$$\tan{\left(\frac{\sqrt{n}}{n} \right)}$$
It is a series of species
$$a_{n} \left(c x - x_{0}\right)^{d n}$$
- power series.
The radius of convergence of a power series can be calculated by the formula:
$$R^{d} = \frac{x_{0} + \lim_{n \to \infty} \left|{\frac{a_{n}}{a_{n + 1}}}\right|}{c}$$
In this case
$$a_{n} = \tan{\left(\frac{1}{\sqrt{n}} \right)}$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{n \to \infty} \left|{\frac{\tan{\left(\frac{1}{\sqrt{n}} \right)}}{\tan{\left(\frac{1}{\sqrt{n + 1}} \right)}}}\right|$$
Let's take the limit
we find
True

False
The rate of convergence of the power series
The answer [src]
  oo            
____            
\   `           
 \       /  1  \
  \   tan|-----|
  /      |  ___|
 /       \\/ n /
/___,           
n = 2           
$$\sum_{n=2}^{\infty} \tan{\left(\frac{1}{\sqrt{n}} \right)}$$
Sum(tan(1/sqrt(n)), (n, 2, oo))
The graph
Sum of series tg(1/nsqrtn)

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