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MathGroup Archive 2000

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Re: Integration...

  • To: mathgroup at smc.vnet.net
  • Subject: [mg24174] Re: Integration...
  • From: Brian Higgins <bghiggins at ucdavis.edu>
  • Date: Wed, 28 Jun 2000 22:50:55 -0400 (EDT)
  • References: <8jc70h$df6@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Matt,
If you know f(a)=f0 and g(a)=g0 and suppose
f'(t)=F(t), and g'(t)=G(t). Then use NDSolve and plot the solution
using ParametricPlot, i.e.

sol=NDSolve[{f'[t]==F[t],g'[t]==G[t],f[a]==f0,g[a]==g0},{f,g},{t,a,b}]
ParametricPlot[Evaluate[{f[t],g[t]}/.sol],{t,a,b}]

You can readily extend this to plot the family of parametric curves
for  a specified range of f0, and g0.

Cheers,

Brian




odIn article <8jc70h$df6 at smc.vnet.net>,
  "Yeung, Matthew" <m.yeung at ic.ac.uk> wrote:
> Dear Sir,
>
> I am a Mathematica user and am having problems with one
particular task that
> I have to perform.
>
> I have 2 function, {f'(t),g'(t)}, that are unintegrable. I wish to plot
the
> parametric curve {f(t),g(t)} for a<t<b, say, but do not wish to use
> NIntegrate as it will give me the result {f(T)-f(a),g(T)-g(a)}.
>
> Is there a way that I can find {f(a),g(a)} so that I can use
NIntegrate; or
> is it possible to evaluate the integral at one point?
>
> Thanks for your heklp and I look forward to hearing from you
soon.
>
> Regards,
>
> Matt Yeung
>
>


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