Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2007
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2007

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Simplification with subscripted variables and anonymous functions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg81618] Re: Simplification with subscripted variables and anonymous functions
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Sat, 29 Sep 2007 02:32:42 -0400 (EDT)
  • Organization: Uni Leipzig
  • References: <fdi6cc$rl8$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de

Hi,

you missunderstand the role of Sum[]. Sum[] try to find a
closed expression for the summation and transform

Sum[1/r^i, {i, 1, Infinity}] to 1/(r-1)

but it makes *no* formal transformations when it
can't find such a closed form. The reason is, that
such a transformation can destroy the convergence of the
Sum[]. You have to wrote your own rules
for the transformations of the sum.

In your second example

FullSimplify[g[p]*g[q], g[p]*g[q] == 0]

work as expected.

Regards
   Jens

Rick Warfield wrote:
> Hi,
> 
> This is probably a very basic question but I wasn't able to find an
> answer in the archives.  I am trying to use Mathematica to combine and
> simplify some sums, for example:
> 
> FullSimplify[ (Sum[Subscript[r, j], {j, 1, n}] - Sum[Subscript[r, k],
> {k, 1, d}])^2, Element[d | n, Integers] && d < n ]
> 
> Is equivalent to
> 
> Sum[Subscript[r, m], {m, k+1, d}]
> 
> But Mathematica doesn't make the simplification.
> 
> A related problem I have is with expressions that use a variable as an
> anonymous function, such as g in the following expression:
> 
> FullSimplify[g[p]*g[q], ForAll[{p, q}, g[p]*g[q] == 0]]
> 
> Should simplify to 0, but does not (of course I could also have
> written this with subscripts, but that also doesn't work)
> 
> Thanks for your help!
> 
> 


  • Prev by Date: Re: Dependence of precision on execution speed of Inverse
  • Next by Date: Re: Simplification with subscripted variables and anonymous functions
  • Previous by thread: Re: Simplification with subscripted variables and anonymous functions
  • Next by thread: git + Mathematica = corrupt notebooks