This is Taylor series of function

My question is:

What is form of ?

Thank you very much!

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- Jun 25th 2010, 02:54 PMAlso sprach ZarathustraA problem!

This is Taylor series of function

**My question is:**

What is form of ?

Thank you very much! - Jun 25th 2010, 05:37 PMAckbeet
Well, the denominators look something like a factorial (except for that pesky 3 in the squared term; perhaps you could massage it to look better). Maybe you could set up a recurrence relation to figure out the numerators?

- Jun 25th 2010, 05:49 PMAlso sprach Zarathustra
Ohhh... it's not 2/3 it's 3/2 :(

Sorry!!!

(I'm going to change it in my original post)

Thank you Mr. Keister! - Jun 25th 2010, 06:11 PMAckbeet
Aha. So it is a nice little factorial in the denominator. Well, the recurrence relation idea sounds nice, but I'm not sure how it would work in principle. Why don't you show all the details of the computations for those first few terms? Maybe something'll pop out.

- Jun 25th 2010, 06:15 PMAlso sprach Zarathustra

You ask for computations ?

Here it is: :) Function calculator

Moreover... look here...

1 3 11 50 - OEIS Search Results - Jun 25th 2010, 06:25 PMAckbeet
No, that's not what I'm interested in. I'm interested in seeing the step-by-step calculations for computing each coefficient. I'm curious to see if a pattern pops out by examining that process.

- Jun 25th 2010, 06:39 PMAlso sprach Zarathustra
Unfortunately, I can't do so, it is very complicated, but the thing I can do is to post the original question asked.

Q.

Find Taylor polynomial of around , find formula for .

Find the radius of convergence of infinite Taylor polynomial(power series). - Jun 25th 2010, 08:32 PMsimplependulum
Hi , it is

- Jun 25th 2010, 08:41 PMAlso sprach Zarathustra
Make sense!

How you get this result please? - Jun 25th 2010, 09:05 PMAlso sprach Zarathustra
So, the radius of convergence of is R=0?

Thanks! - Jun 25th 2010, 09:39 PMsimplependulum
No , the radius is 1 , i obtain the general term by expanding and followed by coefficients' consideration .

- Jun 26th 2010, 01:11 AMchisigma
The general formula for the product of two series is...

(1)

... and in Your case is...

(2)

Kind regards

- Jun 26th 2010, 09:56 AMAlso sprach Zarathustra
I have difficulties in finding radius of convergence! Why it equals to 1?

In other words,**WHY**? - Jun 26th 2010, 10:01 AMAlso sprach Zarathustra
Maybe it from the "sandwich" rule?

so when

- Jun 26th 2010, 10:42 AMtheodds
If exists, then does as well, and they are equal. Since the first expression exists, you can use it to find the radius of convergence, which will work out to be 1.

If you think to calculate from the terms you listed out then it becomes pretty easy to figure out the form of the , though this isn't exactly a rigorous solution.