Re: Evaluating a sum from terms generated by the Array
- To: mathgroup at smc.vnet.net
- Subject: [mg109519] Re: Evaluating a sum from terms generated by the Array
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Mon, 3 May 2010 06:11:31 -0400 (EDT)
Array[((-1)^(# + 1) (x)^#)/#! &, 3, 1] // Total
x^3/6 - x^2/2 + x
Plus @@ Array[((-1)^(# + 1) (x)^#)/#! &, 3, 1]
x^3/6 - x^2/2 + x
Sum[(-1)^(n + 1) x^n/n!, {n, 3}]
x^3/6 - x^2/2 + x
Series[1 - E^-x, {x, 0, 3}] // Normal
x^3/6 - x^2/2 + x
% == %% == %%% == %%%%
True
Bob Hanlon
---- davef <davidfrick2003 at yahoo.com> 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?