MathGroup Archive 2006

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

Search the Archive

How do I create a parametric expression?

  • To: mathgroup at
  • Subject: [mg68537] How do I create a parametric expression?
  • From: axlq at (axlq)
  • Date: Wed, 9 Aug 2006 04:19:05 -0400 (EDT)
  • Sender: owner-wri-mathgroup at

I'm trying to figure out how to simplify a large expression so that it's
expressed in terms of a sub-expression that's factored into the larger

My expression looks like this:

-((1 + 2*n)*((a^4*k^2 + a^2*(-1 + k^2*(q - z)^2) + 2*(q - z)^2)
   *Cos[k*Sqrt[a^2 + (q - z)^2]] - k*(a^2 - 2*(q - z)^2)
     *Sqrt[a^2 + (q - z)^2]*Sin[k*Sqrt[a^2 + (q - z)^2]])
       *Sin[((1 + 2*n)*Pi*z)/L])/(8*Pi*w*(a^2 + (q - z)^2)^(5/2))

Now, I *know* there are places in there were Sqrt[a^2+(q-z)^2] occurs,
either by itself or raised to various powers.  If I want to define


...then how can I make Mathematica re-state my expression in terms
of R?  The ReplaceRepated[] function doesn't seem to do the job.

I need to do this because I am translating the expressions into
Visual Basic code for an Excel application, and it would be nice to
find groupings of terms repeated throughout the expression that I
need to calculate only once.


  • Prev by Date: Re: MemberQ
  • Next by Date: Re: Newbie question about column sums of arrays
  • Previous by thread: RE: need mathematica's help for exploring a certain type of mapping
  • Next by thread: Re: How do I create a parametric expression?