[Maxima] Substitution question

Milan Lukic milan at eskimo.com
Thu Dec 20 23:57:09 CST 2007

Just found a better way then one I emailed a minute ago:)

myv1 : ratsubst(x,Gact*Gth,myvar);
solve(x/(x+1)=Gcl,x);
subst(%,myv1),ratsimp,factor;

hth,
Milan

* Ryan Krauss &lt;ryanlists at gmail.com&gt; [2007-12-20 23:08:22 -0600]:

> I have the following result after some calculations:
>
> myvar:(Gact*Gth*(Ga*s^2*xbeam+thdhat))/(Gact*Gth+1);
>
> I would like to define a new variable Gcl and substitute it for the
> expression Gact*Gth/(Gact*Gth+1) in the above result.  I don't seem to
> be able to do this easily with any substitution commands.  Is there an
> easy way to do this substitution?  The only way I have found is to do
> the following:
>
> Gcl2:Gact*Gth/(Gact*Gth+1);
>
> myvar2:myvar/Gcl2*Gcl;
>
> which produces the desired result:
> Gcl*(Ga*s^2*xbeam+thdhat)
>
> but this would be a very bad approach if it were accidentally applied
> to an expression that didn't already contain the term I am trying to
> factor out.
>
> Any thoughts?
>
> Thanks,
>
> Ryan
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