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## #1 2011-07-30 23:13:40

gAr
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### Series

Problems on partial / infinite series.

Prove that

1)

2)

Deduce that

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #2 2011-07-31 02:04:39

bobbym

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### Re: Series

Hi gAr;

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #3 2011-07-31 02:14:49

gAr
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### Re: Series

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #4 2011-07-31 02:19:08

bobbym

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### Re: Series

Hi gAr;

I know but I could not resist.

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #5 2011-07-31 02:28:02

gAr
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### Re: Series

Okay!

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #6 2011-07-31 02:45:37

bobbym

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### Re: Series

Hi gAr;

Working on it the right way now, will post the answer if I get it.

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #7 2011-07-31 02:50:05

gAr
Star Member

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### Re: Series

Hi,

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #8 2011-07-31 14:59:50

bobbym

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### Re: Series

Hi gAr;

Nothing yet, just some dead ends.

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #9 2011-07-31 15:15:27

gAr
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### Re: Series

Hi bobbym,

Okay,
a

Last edited by gAr (2011-07-31 15:23:58)

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #10 2011-07-31 15:19:58

bobbym

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### Re: Series

Hi gAr;

I do not need the hint yet, have a couple of ideas left. Taking a break to rest. See you them.

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #11 2011-07-31 15:22:32

gAr
Star Member

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### Re: Series

Okay, see you later.

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #12 2011-07-31 19:55:10

bobbym

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### Re: Series

Hi gAr;

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #13 2011-07-31 20:30:57

gAr
Star Member

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### Re: Series

Hi bobbym,

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #14 2011-07-31 20:38:22

bobbym

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### Re: Series

Hi gAr;

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #15 2011-07-31 20:48:57

gAr
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### Re: Series

Okay.

I was confused by W|A's output!

Isn't that always 0?

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #16 2011-07-31 21:00:03

bobbym

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### Re: Series

Hi gAr;

I do not think so. I solved for it as a definite integral:

integrate(log(2*cos(x/2))cos(n*x),{x,-Pi,Pi})/Pi

I just plugged in n = 0, 1, 2, 3, 4, 5

That works at home but Alpha is dogging it.

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #17 2011-07-31 21:07:34

gAr
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### Re: Series

Hi,

Okay.
Could you deduce the sum?

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #18 2011-07-31 21:10:59

bobbym

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### Re: Series

Hi;

To get a feel for the coeficients:

nintegrate(log(2*cos(x/2))*cos(n*x),{x,-Pi,Pi})/Pi

Substitute for n =0,1,2,3,4,5 one at a time.

Could you deduce the sum?

If I have to use 1), so far I do not have any idea how to do it.

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #19 2011-07-31 21:16:46

gAr
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### Re: Series

I have confirmed the coefficients.
In sage, numerical integral is okay, but integral shows 0. Even the sum, for some n, it goes completely wrong!

Do you need a hint or will you try some more time?

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #20 2011-07-31 21:33:12

bobbym

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### Re: Series

Hi gAr;

A hint? I need a doctor! I will try to do it as soon as I finish eating and take a little break.

Thanks for posing the problem.

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #21 2011-07-31 21:36:31

gAr
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### Re: Series

Hi bobbym,

Okay, see you later.
I think I sounded like I was in a hurry, sorry.

You're welcome!

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #22 2011-07-31 22:15:04

bobbym

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### Re: Series

Hi gAr;

No problem, do not worry about it.

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #23 2011-07-31 23:18:23

gAr
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### Re: Series

3)

Find

Last edited by gAr (2011-08-26 20:48:55)

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #24 2011-08-01 15:45:15

gAr
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### Re: Series

4)

This appeared in AMM

Find

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #25 2011-08-01 20:21:16

bobbym

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### Re: Series

Hi;

I have been unable to deduce:

from

Did you have a solution?

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.