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## Re: [Help-gsl] integration

**From**: |
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**Subject**: |
Re: [Help-gsl] integration |

**Date**: |
Mon, 15 May 2006 20:59:32 +0200 |

change of variables needs the integrand to be invertible
over the interval - which is not the case, try it the other
way round (shorten interval to [r,1] and regard periodics)
you should get (1-2*cos(a)+cos(a)^2)/a^2 with a = 10^8.
On 15 May 2006 at 9:49, ghadir mohammadkhani wrote:
>* Dear My friends*
>* I would like to thank you for GNU Scientific Library.*
>* I have a problem in respect to oscillatory integrals.*
>* For example, I want to Integrate from a very simple*
>* function that its solution is perfectly evident*
>* analytically:*
>* Sin(100,000,000*x)*Sin(100,000,000*y) where x and y go*
>* from 0-1. I have done a variable change over x and y,*
>* with this work, x and y go from 0-10^8, since the*
>* sinuous integral at interval 0-2*pi is zero, so I*
>* can choose integral interval as following:*
>* 10^8/(2*pi)-Integer part [10^8/(2*pi)]=0.30919*
>* I have used several subroutines, but unfortunately I*
>* have not obtained an exact result. Now, I wanted to*
>* know whether there is a special way for*
>* these kinds of integrals?*
>* If it is possible for you, Please guide me.*
>* Thank you so much all of frieds for your kind*
>* attention and consideration.*
>* With best regards,*
>* Ghadir Mohammadkhani.*
>* *
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