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R: R: Help.Help.Help.Help

  • To: mathgroup at
  • Subject: [mg15333] R: R: Help.Help.Help.Help
  • From: "Alessandro Ercolani" <alerco at>
  • Date: Fri, 8 Jan 1999 04:15:21 -0500
  • Sender: owner-wri-mathgroup at

[Contact the author to obtain the file mentioned below - moderator]

It's me Alessandro Ercolani.
I'd like to explain well my problem. The file Duff1.bmp is token from
file orbits.nb. It show the evolution of circle of initial condition of
radius r that it follow the Duffing's equation
x''[t]+x'[t]+(x[t]^3)==Cos[t] I thought to put together Duffin's
equation and equation of a circle to calculate parametric equation of
the curve in the picture for every t.  But using Mathematica 3.0 I have
a lot of problems. A important thing is that the evolution of the
Duffing's equation is represented on phase plane so on the axes there
are x[t] and x'[t]. So for example the circle's equation is (x[t]^2) +
(x' [t]^2) + ax[t]+bx' [t]+c==0
Beside I don't have the exact initial conditions because x[0] and x'[0]
don't represent a point but a circle. The only things that I know they
are the center (-1,1) and the radius r=0.3 Can you help me please?
Thanks in advance.

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