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## #1 2016-12-25 16:14:03

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,426
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### Closed form for generating functions

How do I show the following:

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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## #2 2016-12-25 17:40:51

Member
Registered: 2016-04-16
Posts: 982

### Re: Closed form for generating functions

It comes readily from the series expansion of log(1+x) and log(1-x)

{1}Vasudhaiva Kutumakam.{The whole Universe is a family.}
(2)Yatra naaryasthu poojyanthe Ramanthe tatra Devataha
{Gods rejoice at those places where ladies are respected.}

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## #3 2016-12-25 18:05:08

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,115

### Re: Closed form for generating functions

Hi;

Run these.

``````Assuming[x != 1,
FullSimplify[
Log[Sqrt[(1 + x)/(
1 - x)]] == (1/2) Log[(1 + x)/(1 - x)] == (1/
2) (Log[1/(1 - x)] + Log[1 + x])]]``````
``````a = Series[Log[1/(1 - x)], {x, 0, 10}] // Normal
b = Series[Log[1 + x], {x, 0, 10}] // Normal``````
``(1/2) (a + b) // Expand``

Now match that up term by term with your series on the LHS.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #4 2016-12-25 18:51:39

Member
Registered: 2016-04-16
Posts: 982

### Re: Closed form for generating functions

Last edited by thickhead (2016-12-25 19:14:40)

{1}Vasudhaiva Kutumakam.{The whole Universe is a family.}
(2)Yatra naaryasthu poojyanthe Ramanthe tatra Devataha
{Gods rejoice at those places where ladies are respected.}

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## #5 2016-12-26 01:28:26

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,426
Website

### Re: Closed form for generating functions

Thank you guys

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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