Re: NSum working on Re[ ]
- To: mathgroup at smc.vnet.net
- Subject: [mg43034] Re: NSum working on Re[ ]
- From: Mathijs Romans <m.w.j.romans at phys.uu.nl>
- Date: Sat, 9 Aug 2003 02:57:35 -0400 (EDT)
- Organization: Academic Computer Centre Utrecht, (ACCU)
- References: <bgv8md$58b$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Thank you for your response, but it does not solve the problem for me.
While I was trying to focus on the problem, I gave a simplified version
of the issue. For my problem, I do not think there is a workaround:
NSum[(1 + Re[Sqrt[1 - I n]]) / ((n + Im[Sqrt[1 - I n]])^2 + (1 +
Re[Sqrt[1 - I n]])^2) , {n, 1, Infinity}]
gives a similar error, due to the derivative of Re[] being unknown...
Regards,
Mathijs Romans
Utrecht, the Netherlands
Andrzej Kozlowski wrote:
> This is a curious problem as
>
>
> NSum[Re[Sqrt[n + I]], {n, 1, 24}]
>
> 80.879
>
> works fine but
>
> In[270]:=
> NSum[Re[Sqrt[n + I]], {n, 1, 25}]
>
> gives the error message about the derivative or Re[...] at n= 16 (!)
>
> However, you can avoid this problem by using simply:
>
>
> Re[NSum[Sqrt[n + I], {n, 1, 100}]]
>
> 671.734
>
> Andrzej Kozlowski
> Yokohama, Japan
> http://www.mimuw.edu.pl/~akoz/
> http://platon.c.u-tokyo.ac.jp/andrzej/