Dear Nils,

Thanks for the careful explanation.  There's a good reason I don't teach 
this stuff (even if I enjoy it!).

Rob

On Thursday, November 5, 2015 at 7:35:47 PM UTC-8, Nils Bruin wrote:
>
> On Thursday, November 5, 2015 at 5:11:42 PM UTC-8, Rob Beezer wrote:
>>
>> LIke I said, my complex analysis is rusty.  And I am really asking for 
>> somebody else.  Is the chunk of code that produces 2 (above) not following 
>> the definition of the residue?
>>
>
> No it's not. If t=1/z then you don't get a truncated taylor expansion 
> around t=0 by substituting t=1/z in the taylor expansion around z=0.
>
> In general, if you define the residue by a contour integral, then the 
> residue of exp(1/z) around z=0 is 0: Any contour around z=0 is a boundary 
> of a simply connected domain of the Riemann sphere on which the function is 
> regular, so integrating along the contour gets you 0.
>
> exp(1/z) has an essential singularity at z=0, so there is no laurent 
> expansion to read off the residue from.
>

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