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#26 2011-07-17 08:23:57
- bobbym
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Re: Tricky integral of a rational function
Hi gAr;
I do not know who put that integral together. I do know that there is a paper out there on doing that integral. I was unable to get it because it was in a journal that was not free.
Thanks for providing that page!
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#27 2011-07-17 20:41:44
- gAr
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Re: Tricky integral of a rational function
Hi bobbym,
It's solved in a journal??
A.M.M?
"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."
#28 2011-07-17 20:57:20
- bobbym
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Re: Tricky integral of a rational function
Hi gAr;
I saw it when this problem was first posed here. Unfortunately I was not following my signature strictly at the time. I wrote nothing down and soon forgot when and where.
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#29 2011-07-17 21:11:30
- gAr
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Re: Tricky integral of a rational function
Oh, 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."
#30 2011-07-17 21:18:58
- bobbym
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Re: Tricky integral of a rational function
Hi;
All I can remember from the abstract was that this one could be done by hand but only by a few.
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#31 2011-07-17 21:34:26
- gAr
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Re: Tricky integral of a rational function
How can they say it can be done only by a few?!
"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."
#32 2011-07-17 21:41:57
- bobbym
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Re: Tricky integral of a rational function
Hi gAr;
I guess they mean if the person does not know 10000 theorems in topology, he/she does not have a chance.
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#33 2011-07-17 21:54:35
- gAr
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Re: Tricky integral of a rational function
Hi bobbym,
Maybe.
Anyway, I'll check with what I know for now.
Looks like we need to use "landen transformations", and I do not understand it yet.
Last edited by gAr (2011-07-18 01:07:11)
"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."
#34 2011-07-18 18:50:50
- bobbym
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Re: Tricky integral of a rational function
Hi gAr;
I have been working on reducing the order of the polynomials but keeping the area under the curve invariant.
Have not had much luck.
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#35 2011-07-18 19:24:41
- gAr
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Re: Tricky integral of a rational function
Hi bobbym,
Okay.
Do you know "landen transformations"? I do not understand it yet. It's full of similar integrals, but I can't find a good example.
"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."
#36 2011-07-18 19:49:40
- bob bundy
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Re: Tricky integral of a rational function
hi bobbym and gAr
The factorisation of
is
where the values are approximately
a = 0.709546081
b = 0.339510641
c = 0.562755113
d = 0.111761451
e = 2.14679097
f = 0.548727908
That’s as close as I can get.
Now, can someone explain Cauchy to me please?
Bob
994
Last edited by bob bundy (2011-07-18 20:05:23)
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#37 2011-07-18 20:51:47
- bobbym
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Re: Tricky integral of a rational function
Hi Bob;
I am getting a residue of zero for all 3 singularities. So something is wrong!
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#38 2011-07-18 21:01:40
- bob bundy
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Re: Tricky integral of a rational function
hi bobbym,
Nice to hear from you today. It looks like this morning's posts need a 'spring clean'.
This bit of complex theory is not yet in my brain. I'd like you to explain what you are doing please.
Now, can someone explain Cauchy to me please?
Also are you able to check the factorisation by multiplying it out in Mathematica for me?
Thanks, 
Bob
996
Last edited by bob bundy (2011-07-18 21:04:34)
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#39 2011-07-18 21:13:51
- bobbym
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Re: Tricky integral of a rational function
Hi Bob;
I have a migraine so I am slower than usual.
Also are you able to check the factorisation by multiplying it out in Mathematica for me?
That is the easy part.
This the formula I am trying to use.
But if each residue is 0 then the sum of all of them will be 0.
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#40 2011-07-18 21:24:09
- gAr
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Re: Tricky integral of a rational function
Hi bobbym,
Since they are approximate values, can it yield a residue?
"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."
#41 2011-07-18 21:27:51
- bobbym
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Re: Tricky integral of a rational function
Hi gAr;
But only an approximate one? We do not have to worry about it because all the residues are equal to 0. The sum of them is 0 and that means the integral is 0, which is false.
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#42 2011-07-18 21:35:43
- gAr
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Re: Tricky integral of a rational function
Hi,
Okay.
Did you try NResidue[] or Residue[] ?
I thought since finding residue is also numerical, we can settle for numerical integration!
Anyway, did you check "landen's transformation"?
http://library.msri.org/books/Book55/files/13landen.pdf
There are many other similar files.
"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."
#43 2011-07-18 21:42:42
- bobbym
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Re: Tricky integral of a rational function
Hi gAr;
I did not check out landens transformations yet. I have a whole book here of transformations to handle rational integrands. I was unable to get any of them to work.
I used Residue[]. I do not think I am using the correct formula.
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#44 2011-07-18 22:07:12
- gAr
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Re: Tricky integral of a rational function
Hi bobbym,
Okay.
By some substitutions, I found that these three are also equivalent:
Can't proceed, though!
"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."
#45 2011-07-18 22:23:37
- bobbym
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Re: Tricky integral of a rational function
Hi gAr;
I read the PDF you found. I can not get any of that to work unless I can see an example done from start to finish. They do not provide one that I can follow.
I started with this partial fraction and worked with the 6th degree denominators.
I never got anywhere.
What did you do to get yours?
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#46 2011-07-18 22:31:07
- gAr
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Re: Tricky integral of a rational function
I can not get any of that to work unless I can see an example done from start to finish.
That's my problem too, no complete example...
I substituted 1/x for x.
The other two, used the partial fractions you wrote.
Subs. y for x+1, and y for x-1 in the other, and recombined.
After deriving that, substitute y by its reciprocal.
Last edited by gAr (2011-07-18 22:32:41)
"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."
#47 2011-07-18 22:40:13
- bobbym
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Re: Tricky integral of a rational function
That's my problem too, no complete example...
I can not stand that. It is so frustrating. The book I have is full of incomplete examples. I can get very little from it. I never mentioned it but I consider that worse than the odd numbered exercises.
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#48 2011-07-18 22:43:33
- gAr
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Re: Tricky integral of a rational function
And one day even the authors cannot understand it, when they forget.
"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."
#49 2011-07-18 23:26:07
- bobbym
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Re: Tricky integral of a rational function
True! But at least they did know at one time. Thanks to the way they do the example their readers will never know!
I can get the denominator down to a degree 10. Are these transformations trying to reduce the integrand to a quadratic one. Or are they trying to produce an integrand that splits into partial fractions?
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#50 2011-07-18 23:35:39
- gAr
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Re: Tricky integral of a rational function
How would people feel if the journals they buy also contain stuff like that?!
I'm not sure what the transformations do. It just looks like the coefficients are changed!
"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."