Mister Exam
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- Taylor Series Step by Step
- Fourier series step by step
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- Product of series
-
How to use it?
- Sum of series:
-
(6+(-4)^n)/(7^(n+2))
-
cos(sqrt(n))/n!
-
2,1
- (xi+2)
-
Identical expressions
- cos(sqrt(n))/n!
- co sinus of e of ( square root of (n)) divide by n!
- cos(√(n))/n!
- cossqrtn/n!
- cos(sqrt(n)) divide by n!
Sum of series cos(sqrt(n))/n!
The solution
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oo ____ \ ` \ / ___\ \ cos\\/ n / / ---------- / n! /___, n = 1
$$\sum_{n=1}^{\infty} \frac{\cos{\left(\sqrt{n} \right)}}{n!}$$
Sum(cos(sqrt(n))/factorial(n), (n, 1, oo))
The radius of convergence of the power series
Given number:
$$\frac{\cos{\left(\sqrt{n} \right)}}{n!}$$
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
$$a_{n} = \frac{\cos{\left(\sqrt{n} \right)}}{n!}$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{n \to \infty} \left|{\frac{\cos{\left(\sqrt{n} \right)} \left(n + 1\right)!}{\cos{\left(\sqrt{n + 1} \right)} n!}}\right|$$
Let's take the limit
we find
$$1 = \lim_{n \to \infty} \left|{\frac{\cos{\left(\sqrt{n} \right)} \left(n + 1\right)!}{\cos{\left(\sqrt{n + 1} \right)} n!}}\right|$$
$$\frac{\cos{\left(\sqrt{n} \right)}}{n!}$$
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
$$a_{n} = \frac{\cos{\left(\sqrt{n} \right)}}{n!}$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{n \to \infty} \left|{\frac{\cos{\left(\sqrt{n} \right)} \left(n + 1\right)!}{\cos{\left(\sqrt{n + 1} \right)} n!}}\right|$$
Let's take the limit
we find
$$1 = \lim_{n \to \infty} \left|{\frac{\cos{\left(\sqrt{n} \right)} \left(n + 1\right)!}{\cos{\left(\sqrt{n + 1} \right)} n!}}\right|$$
False
The rate of convergence of the power series
The graph
Examples of finding the sum of a series
- The Sum of the Power Series
x^n/n
(x-1)^n
- Factorial
1/2^(n!)
n^2/n!
x^n/n!
k!/(n!*(n+k)!)
- Flint Hills Series
csc(n)^2/n^3
- Basel problem
1/n^2
1/n^4
1/n^6
- Harmonic series
1/n
- Grandi's series
(-1)^n
- Alternating series
(-1)^(n + 1)/n
(n + 2)*(-1)^(n - 1)
(3*n - 1)/(-5)^n
(-1)^(n - 1)*n/(6*n - 5)
- Newton–Mercator series
(-1)^(n + 1)/n*x^n
- Exam the series for convergence
(3*n - 1)/(-5)^n