Re: solve output "problem"
- To: mathgroup at smc.vnet.net
- Subject: [mg59659] Re: solve output "problem"
- From: Paul Abbott <paul at physics.uwa.edu.au>
- Date: Tue, 16 Aug 2005 04:56:58 -0400 (EDT)
- Organization: The University of Western Australia
- References: <dc76fj$jrc$1@smc.vnet.net> <dchnth$7vb$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
In article <dchnth$7vb$1 at smc.vnet.net>,
Selina <yedekaccount at hotmail.com> wrote:
> Actually, I was looking for a way to get a symbolic representation of the
> roots which I could then see how they change with respect to some parameters,
> so NSolve wasn't my first choice. But I guess I'll have to resort to that.
I don't understand your conclusion. Root _is_ a symbolic representation
of the root and it does allow you to see how they change with respect to
some parameters. For example, here is a simple polynomial involving one
parameter, a.
sol = Solve[x^5 + a x + 1 == 0, x]
For the first root,
r[1][a_] = x /. sol[[1]]
Here we plot r[1][a] for -5 < a < 4.
Plot[r[1][a], {a, -5, 4}]
Also, let's compute the derivative of this root with respect to a.
dr[1][a_] = D[r[1][a], a]
Note that this is an exact symbolic representation of the derivative.
(It can be reduced to a root of a 5th order polynomial, but RootReduce
or FullSimplify cannot do this simplification).
Here we plot dr[1][a] for -5 < a < 4.
Plot[dr[1][a], {a, -5, 4}]
Cheers,
Paul
--
Paul Abbott Phone: +61 8 6488 2734
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