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Re: error with Sum and Infinity

  • To: mathgroup at smc.vnet.net
  • Subject: [mg102252] Re: [mg102245] error with Sum and Infinity
  • From: Tomas Garza <tgarza10 at msn.com>
  • Date: Mon, 3 Aug 2009 05:44:43 -0400 (EDT)
  • References: <200908021001.GAA01730@smc.vnet.net>

Hello, tb:


 I suggest you use the following definition of t:



t[i_]:=If[i==3,1,0]



Then you'll get what you expect:



Sum[t[i],{i,1,10}]
Out[2]= 1


In[3]:= Sum[t[i],{i,1,Infinity}]
Out[3]= 1





Tomas


> Date: Sun, 2 Aug 2009 06:01:39 -0400
> From: tommaso.biancalani at gmail.com
> Subject: [mg102245] error with Sum and Infinity
> To: mathgroup at smc.vnet.net
>
> Hi experts,
>
> i'm very new to Mathematica and this is my first problem. I define a
> function that is 0 everywhere:
> t[i_] := 0
> expect for point i =3 that is:
> t[3] = 1
> If now i evaluate the finite sum i obtain 1 as expected
> Sum[ t[i], {i, 1, 10}]
> Out = 1
> but if i try do the same with infinity i obtain
> In[808]:= Sum[ t[i], {i, 1, Infinity}]
> Out[808]= 0
> instead of 1 expected. Any advice?
>
> tb
>


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