Re: Sum
- To: mathgroup at smc.vnet.net
- Subject: [mg55250] Re: [mg55175] Sum
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Thu, 17 Mar 2005 03:30:33 -0500 (EST)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
Sum[Exp[-k],{k,0,Infinity}]
E/(-1 + E)
As stated in the Help entry for Sum, Sum evaluates its arguments in a non-
standard way. Use Evaluate:
x=Exp[-k];
Sum[Evaluate[x],{k,0,Infinity}]
E/(-1 + E)
Bob Hanlon
>
> From: mjumbo <mjumbo at nm.ru>
To: mathgroup at smc.vnet.net
> Date: 2005/03/16 Wed AM 05:35:51 EST
> To: mathgroup at smc.vnet.net
> Subject: [mg55250] [mg55175] Sum
>
> Can sombody explain me why
>
> Sum[Exp[- k], {k, 0, Infinity}]
>
> gives the correct result, while the following (imho equivalent) statements
>
> x = Exp[-k]
> Sum[x, {k, 0, Infinity}]
>
> don't? What should I do to make it work? It is rather vexing to copy/paste
long expressions instead of using short placeholders like x.
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>