Re: How do I create a parametric expression?
- To: mathgroup at smc.vnet.net
- Subject: [mg68608] Re: How do I create a parametric expression?
- From: axlq at spamcop.net (axlq)
- Date: Fri, 11 Aug 2006 04:40:47 -0400 (EDT)
- References: <200608090819.EAA21141@smc.vnet.net> <ebec2n$lic$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
In article <ebec2n$lic$1 at smc.vnet.net>,
gardyloo <gardyloo at mail.wsu.edu> wrote:
> I think this question comes up pretty often on the list; it seems to
>be one of the harder things to do (or do well, and consistently) with
>Mathematica. Usually, it seems that people have to delve into the
>FullForm expressions, which can be a huge pain.
Yes, from the responses posted to my original query, it seems
that there is no straightforward way to do it than by making
substitutions one step at a time.
Yours is the most efficient suggestion yet, doing most of it in one
step:
>In[9]:=
>expr //. {(a^2 + (q - z)^2)^(n_) -> R^(2*n)}
>
>Out[9]=
>
>-((1/(8*Pi*R^5*w))*((1 + 2*n)*
> ((a^4*k^2 + a^2*(-1 + k^2*(q - z)^2) + 2*(q - z)^2)*
> Cos[k*R] - k*R*(a^2 - 2*(q - z)^2)*Sin[k*R])*
> Sin[((1 + 2*n)*Pi*z)/L]))
...and as others have suggested, replacing (q-z)^2 by R^2-a^2 takes
it a bit further.
-Alex
- References:
- How do I create a parametric expression?
- From: axlq@spamcop.net (axlq)
- How do I create a parametric expression?