Subject: FW: [ maxima-Bugs-1051437 ] Trig integral error
From: Billinghurst, David (CALCRTS)
Date: Wed, 17 Nov 2004 08:36:17 +1100
> Raymond Toy <raymond.toy@ericsson.com> writes:
>
> [The integral of
> 2*COT(x)^2*COS(2*x)/(CSC(2*x)+COT(2*x));
> is wrong]
>
>> David> This bug is annoying me enough to want to try and fix it.
>> David> Any thoughts on where to start looking?
>>
>> integrate calls sinint in sin.lisp.
>
> Actually, the integral is solved by RISCHINT and friends, who
> EXPONENTIALIZE the integrand, so that it is amenable to the
> hyperexponential case of the Risch algorithm
>
> ...
> Indeed, most of the basic code we need does work for negative
> exponents as well, so I am thinking of a simple-minded fix like
>
> http://members.inode.at/wjenkner/maxima/rat3a.lisp.diff
>
> ...
>
> Please note that all of this is very tentative at the moment.
>
> Wolfgang
I tested Wolfgang's patch. It worked for me, and did not cause any
regressions in the testsuite or the share/contrib/diffequations
testsuite (once they were downcased).
I can't comment on the patch itself. I have borrowed a copy of
Bronstein, but Chapter 5.9 is a long way into the book. Interesting
reading though, and it has helped with another problem I have.
David
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