Re: Symbolic summation
- To: mathgroup at smc.vnet.net
- Subject: [mg101595] Re: Symbolic summation
- From: Peter Breitfeld <phbrf at t-online.de>
- Date: Fri, 10 Jul 2009 23:22:23 -0400 (EDT)
- References: <h3761n$f3i$1@smc.vnet.net>
Luca wrote:
> Hello all, I have a problem, I've to compute a symbolic summation,
> which takes a very long time if I have to do it by hand. I have to
> write the terms of the Volterra series, related to the associated
> linear equation of a system.
>
> The problem is that I'm not really confident with mathematica, I've
> tried to use symbolic calculations with sums, but I think that in my
> case is not so easy.
>
> The problem is that I want a solution of this form:
>
> x1+x2+x3+x4+x5...
>
> Where the 1, 2, 3 and 4 and 5 are the summation subscripts...
>
> My summation is not infinite, I have to stop it.
>
> If I write something like this:
>
> n = 3;
>
> Sum[kl, {l, 2, n}]
>
> I obtain 2kl, instead I want to obtain k2+k3.
>
> Is it possible with mathematica?
>
Luca,
kl is one symbol for Mathematica, so your input of Sum[kl,{l,2,n}] will
be evaluated to kl+kl.
You have to make l a variable, like this:
Sum[k[l],{l,2,3}]
or
Sum[Subscript[a, l], {l, 2, 10}]
--
_________________________________________________________________
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de