Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2008

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

Search the Archive

Re: A Problem with Simplify

  • To: mathgroup at smc.vnet.net
  • Subject: [mg87490] Re: A Problem with Simplify
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Fri, 11 Apr 2008 01:48:47 -0400 (EDT)
  • References: <ftkb7f$a9m$1@smc.vnet.net>

Hi,

the problem is Integrate[] and not simplify because

Integrate[Sin[(n*Pi*x)/L]*Sin[(n*Pi*x)/L], {x, 0, L}]

is different from

Integrate[Sin[(m*Pi*x)/L]*Sin[(n*Pi*x)/L], {x, 0, L}]

and Mathematica should integrate twice.

Regards
   Jens


Kevin J. McCann wrote:
> I have the following rather simple integral of two sines, which should 
> evaluate to zero if m is not equal to n and to L/2 if they are the same.
> 
> The following is just fine
> 
> Imn = Simplify[Integrate[
>         Sin[(m*Pi*x)/L]*
>           Sin[(n*Pi*x)/L],
>         {x, 0, L}]]
> 
> 
> However, if I specify that m and n are integers, I only get the 
> "general" solution of zero, i.e. when m and n are not equal.
> 
> Imn = Simplify[Integrate[
>         Sin[(m*Pi*x)/L]*
>           Sin[(n*Pi*x)/L],
>         {x, 0, L}],
>       Element[m, Integers] &&
>         Element[n, Integers]]
> 
> The workaround is obvious in this case, but shouldn't Mathematica give multiple 
> answers? Perhaps something similar to what it already does with Integrate?
> 
> Kevin


  • Prev by Date: ContourPlot, etc.: not every point a Real
  • Next by Date: Re: A Problem with Simplify
  • Previous by thread: Re: A Problem with Simplify
  • Next by thread: Re: A Problem with Simplify