diff eqts and 3D curves

*To*: mathgroup at smc.vnet.net*Subject*: [mg21878] diff eqts and 3D curves*From*: macsoft <macsoft at ctrlaltdel.ch>*Date*: Wed, 2 Feb 2000 22:54:34 -0500 (EST)*Organization*: UNET/Urbanet NNTPcache news server*Sender*: owner-wri-mathgroup at wolfram.com

Hi! Q1: I have a system of two non-linear 2nd-order differential equations in terms of x(t), x'(t), x''(t), y(t), y'(t), t The system is not very unstable, but near zero the values are out of the range of the machine. I thought it wouldn't matter since I integrate from t = 66 to 72 with initial conditions at t = 66, but I get this message: NDSolve::"ndnum": "Encountered non-numerical value for a derivative at t == 2.524140890933554`*^-299." Does Mathematica always intergate from 0 even if the range asked for is far from 0? If so, how can I avoid that problem? Since my solutions should all funnel to the same kind of behavior at very large t, it is clearly unstable to integrate with final conditions! Q2: I wonder how I can plot a 3D curve, in particular the curve given by: (Re(f(t)),Im(f(t),t) Thank you for your help! macsoft