Re: Solving stiff differential equations
- To: mathgroup at smc.vnet.net
- Subject: [mg84501] Re: Solving stiff differential equations
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Sat, 29 Dec 2007 20:03:27 -0500 (EST)
- References: <fl4utf$9vb$1@smc.vnet.net>
Hi,
scale the x[t] value to y[t]=x[t]/M ??
Regards
Jens
dkjk at bigpond.net.au wrote:
> Hi all,
>
> I want to solve the following nonlinear ODE
>
> x'[t] == M - 3 x[t] Sqrt[-M*t + 7/10 + x[t]]
>
> x[0] == 3/10
>
> where M is a very large number (~10^43).
>
> I tried solving this using
>
> M = 10^43;
> s = NDSolve[{x'[t] == M - 3 x[t] Sqrt[-M t + 7/10 + x[t]],
> x[0] == 3/10}, x[t], {t, -10, 10}, WorkingPrecision -> 20]
> Plot[Evaluate[x[t] /. s], {t, -10, 10}, PlotRange -> All]
>
> but I got a lot of errors. Could anyone please advise how I should go
> about solving this?
>
> Best regards,
> James
>