>
> 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.  This is now tracked 
at http://trac.sagemath.org/ticket/16224.

 

> For other sums, Sage simply repeats what I told it.
>
> sum(x^(3*k)/factorial(2*k),k,0,oo)
>
> I understand that Sage has limited exploitation of Maxima's hypergeometric 
> functionality, and I suspect this is the main issue. Are there any 
> conceivable workarounds?
>
>
Yeah, that is definitely part of it.  See e.g 
http://trac.sagemath.org/ticket/9908 .

- kcrisman

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