Thank you.

On Monday, September 7, 2015 at 10:52:12 AM UTC+3, Kalevi Suominen wrote:
>
>
>
> On Monday, September 7, 2015 at 9:37:58 AM UTC+3, Paul Royik wrote:
>>
>> I see this error when try to calculate limit of (-1)^x /sqrt(x) as x 
>> approaches infinity.
>> Can somebody explain me what is the problem here?
>>
>
> ``(-1)^x`` is equal to ``exp(pi*I*x)``. As the function has no serial 
> expansion at infinity, SymPy attempts to use Gruntz' algorithm. It is 
> intended tor real functions, and SymPy assumes that everything is real. It 
> knows that ``pi`` is real and positive and the same is assumed of ``x``. 
> That leaves just one problem: what is the sign of I.
>
> Actually, there is currently no algorithm in SymPy capable of computing 
> the limit (which is 0 as ``x`` tends to ``oo`` on the real line), 
>

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