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(-1)^n+1/(2n+1)!

Sum of series (-1)^n+1/(2n+1)!



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The solution

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  oo                      
 ___                      
 \  `                     
  \   /    n       1     \
   )  |(-1)  + ----------|
  /   \        (2*n + 1)!/
 /__,                     
n = 1                     
n=1((1)n+1(2n+1)!)\sum_{n=1}^{\infty} \left(\left(-1\right)^{n} + \frac{1}{\left(2 n + 1\right)!}\right)
Sum((-1)^n + 1/factorial(2*n + 1), (n, 1, oo))
The radius of convergence of the power series
Given number:
(1)n+1(2n+1)!\left(-1\right)^{n} + \frac{1}{\left(2 n + 1\right)!}
It is a series of species
an(cxx0)dna_{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:
Rd=x0+limnanan+1cR^{d} = \frac{x_{0} + \lim_{n \to \infty} \left|{\frac{a_{n}}{a_{n + 1}}}\right|}{c}
In this case
an=(1)n+1(2n+1)!a_{n} = \left(-1\right)^{n} + \frac{1}{\left(2 n + 1\right)!}
and
x0=0x_{0} = 0
,
d=0d = 0
,
c=1c = 1
then
1=limn(1)n+1(2n+1)!(1)n+1+1(2n+3)!1 = \lim_{n \to \infty} \left|{\frac{\left(-1\right)^{n} + \frac{1}{\left(2 n + 1\right)!}}{\left(-1\right)^{n + 1} + \frac{1}{\left(2 n + 3\right)!}}}\right|
Let's take the limit
we find
True

False
The rate of convergence of the power series
1.07.01.52.02.53.03.54.04.55.05.56.06.51-1
The graph
Sum of series (-1)^n+1/(2n+1)!

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