On Sat, Aug 30, 2008 at 6:06 AM, tkeller <[EMAIL PROTECTED]> wrote:
>
> I asked this question myself a few months ago, and the easiest 2
> solutions seem to be utilizing sympy or maxima.
>
> Via sympy it is:
> import sympy
> sympy.var('x')
> print sympy.sum(2**(-x), (x, 1, oo))
>
> I'm taking this from a question I posed on the sympy message list:
> http://groups.google.com/group/sympy/browse_frm/thread/5348ded3ebe8a25e?tvc=1
>
> It should return a result of 1, but in sage 3.1.1 it returns 1-2*2**(1-
> Infinity). While technically correct, this should clearly return 1
> when simplified so I guess there is some complication when
> transferring between modules. Ondrej will assuredly give more useful
> information if he sees this.
sympy returns 1 for me:
In [1]: sum(2**(-x), (x, 1, oo))
Out[1]: 1
>
> More specifically , your example using m=2 is:
> sympy.sum(1/((x+2)**3)),(x,1,oo))
>
> Unfortunately this returns
> Sum((2 + x)**(-3), (x, 1, Infinity))
In [4]: sum(1/(x+2)**3,(x,1,oo))
Out[4]: Sum((2 + x)**(-3), (x, 1, oo))
Thanks for the spot, I reported it:
http://code.google.com/p/sympy/issues/detail?id=1066
>
> n() on this function does not work, maybe a sympy equivalent would?
> It may work better with a %python header, though I haven't tested this
> yet (if you use the notebook).
It does work in sympy:
In [5]: N(sum(1/(x+2)**3,(x,1,oo)))
Out[5]: 0.0770569031595943
is this the correct result? If not, could you please report it in our issues?
It would help a lot, thanks,
Ondrej
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