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Re: Evaluating a sum from terms generated by the Array

  • To: mathgroup at smc.vnet.net
  • Subject: [mg109521] Re: Evaluating a sum from terms generated by the Array
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Mon, 3 May 2010 06:11:53 -0400 (EDT)

Very simple:

   Apply[Plus, Array[((-1)^(# + 1) (x)^#)/# !&, 3, 1 ]]

Or, using the prefix @@ abbreviation for Apply:

   Plus @@ Array[((-1)^(# + 1) (x)^#)/#! &, 3, 1]

Or, with a newer specialized function in Mathematica:

   Total[Array[((-1)^(# + 1) (x)^#)/#! &, 3, 1]]

Or:

   Total @ Array[((-1)^(# + 1) (x)^#)/#! &, 3, 1]

On 5/2/2010 5:35 AM, davef wrote:
> I want to evaluate a sum from a series I created using the Array
> function.
>
> For example; I specify
>
> Array[((-1)^(# + 1) (x)^#)/# !&, 3, 1 ]
>
> which gives me the following 3 terms of output:
>
> {x, -(x^2/2), x^3/6}
>
> Can anyone tell if and how I can turn these 3 terms into a sum to be
> evaluated?
>

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305


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