#16224: incorrect translation of Bessel from Maxima?
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Reporter: kcrisman | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.2
Component: calculus | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Description changed by kcrisman:
Old description:
> From [https://groups.google.com/forum/#!topic/sage-support/IgC78rcdO7c
> this sage-suppot thread}:
> {{{
> But other sums are simply wrong.
>
> k = var('k')
> sum(x^(2*k)/factorial(2*k),k,0,oo)
>
> gives
>
> -1/4*sqrt(2)*sqrt(pi)*x^(3/2)
>
> but the answer should be sinh(x).
>
> Hmm. That shouldn't be happening, though I wouldn't be surprised if it
> didn't turn out as easy as that.
>
> (%i1) load(simplify_sum);
> (%o1) /Users/.../Sage-5.12-OSX-64bit-10.6.app/Contents/Reso\
> urces/sage/local/share/maxima/5.29.1/share/solve_rec/simplify_sum.mac
> (%i3) display2d:false;
>
> (%o3) false
> (%i4) simplify_sum(sum(x^(2*k)/factorial(2*k),k,0,inf));
>
> (%o4) sqrt(%pi)*bessel_i(-1/2,x)*sqrt(x)/sqrt(2)
>
> So I'm not sure why that would happen - maybe because of incorrect Bessel
> simplification?
>
> sage: maxima_calculus('bessel_i(-1/2,x)')
> bessel_i(-1/2,x)
> sage: _._sage_()
> sqrt(2)*sqrt(1/(pi*x))*cosh(x)
>
> That gives cosh(x), which I think is what you meant.
> }}}
> I don't know why this would happen, but presumably it should be possible
> to track down without too much effort.
New description:
From [https://groups.google.com/forum/#!topic/sage-support/IgC78rcdO7c
this sage-support thread]:
{{{
But other sums are simply wrong.
k = var('k')
sum(x^(2*k)/factorial(2*k),k,0,oo)
gives
-1/4*sqrt(2)*sqrt(pi)*x^(3/2)
but the answer should be sinh(x).
Hmm. That shouldn't be happening, though I wouldn't be surprised if it
didn't turn out as easy as that.
(%i1) load(simplify_sum);
(%o1) /Users/.../Sage-5.12-OSX-64bit-10.6.app/Contents/Reso\
urces/sage/local/share/maxima/5.29.1/share/solve_rec/simplify_sum.mac
(%i3) display2d:false;
(%o3) false
(%i4) simplify_sum(sum(x^(2*k)/factorial(2*k),k,0,inf));
(%o4) sqrt(%pi)*bessel_i(-1/2,x)*sqrt(x)/sqrt(2)
So I'm not sure why that would happen - maybe because of incorrect Bessel
simplification?
sage: maxima_calculus('bessel_i(-1/2,x)')
bessel_i(-1/2,x)
sage: _._sage_()
sqrt(2)*sqrt(1/(pi*x))*cosh(x)
That gives cosh(x), which I think is what you meant.
}}}
I don't know why this would happen, but presumably it should be possible
to track down without too much effort.
--
--
Ticket URL: <http://trac.sagemath.org/ticket/16224#comment:1>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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