Another interesting data point - in Maxima itself:
(%i6) display2d:false;
(%o6) false
(%i7) limit(-(3*n^2 + 1)*(-1)^n/sqrt(n^5 + 8*n^3 + 8),n,inf);
(%o7) -38*und*log(-1)^2/25
But in Sage
sage: log(-1)
I*pi
which presumably leads to this.
Dan, I'm on a train with horrible internet - can you open a ticket, post to
the Maxima list, etc.? Thanks!
On Friday, November 8, 2013 4:31:34 PM UTC-5, Dan Drake wrote:
>
> On Fri, 08 Nov 2013 at 01:03PM -0800, kcrisman wrote:
> > Note the "und" - undefined. Maxima is probably noticing the (-1)^n
> piece...
>
> I'm not sure it's the (-1)^n. I tried using cos(pi*n) instead and still
> get "und":
>
> sage: n = var('n')
> sage: assume(n>0)
> sage: series = -(3*n^2 + 1)*cos(pi*n)/sqrt(n^5 + 8*n^3 + 8)
> sage: limit(series, n=infinity)
> 6/5*pi*und + 2/5*und
>
> But observe:
>
> sage: series = -(1)*cos(pi*n)/sqrt(n^5 + 8*n^3 + 8)
> sage: limit(series, n=infinity)
> 0
>
> (It also works with (-1)^n.)
>
> It looks like Maxima is actually getting confused by the n^2 in the
> denominator. Not sure what it's doing to find the limit.
>
>
> Dan
>
> --
> --- Dan Drake
> ----- www.math.wisc.edu/~ddrake/
> -------
>
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