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MathGroup Archive 2005

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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.
> __________
> www.newmail.ru -- Íîâàÿ Ïî÷òà: âñå ïî-íîâîìó.
> 
> 


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