       Re: System of differential equations

• To: mathgroup at smc.vnet.net
• Subject: [mg128992] Re: System of differential equations
• From: Hazem AbdelHafiz <hazem.abdelhafiz at gmail.com>
• Date: Fri, 7 Dec 2012 01:39:33 -0500 (EST)
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• References: <20121206095813.308946374@smc.vnet.net> <CAEtRDSdqn65NArwmJS7JDq=vn0gGSqkni5kWNKZbE9C2f7LG-w@mail.gmail.com>

```Thanks Bob,
Thanks for the fast comment
It now solves

On Fri, Dec 7, 2012 at 1:34 AM, Bob Hanlon <hanlonr357 at gmail.com> wrote:

> The Sin functions must be entered as Sin vice sin. The range of t is
> too large to be handled.
>
> s = NDSolve[{
>     ph1''[t] + ph1'[t] + Sin[ph1[t]] - mu[t] - mu'[t] == 0.005,
>     ph2''[t] + ph2'[t] + Sin[ph2[t]] + mu[t] + mu'[t] == 0.005,
>     0.2 mu'[t] + mu[t] == ph1'[t] - ph2'[t], ph2 == 0, ph1 == 0,
>     ph2' == 0, ph1' == 0, mu == 0},
>    {ph1[t], ph2[t], mu[t]},
>    {t, 0, 240}];
>
> Plot[Evaluate[Tooltip[#, ToString[#]] & /@
>     {ph1[t], ph2[t], mu[t]} /. s],
>  {t, 0, 10},
>  Frame -> True, Axes -> False]
>
> However, the range on t affects the results
>
> s = NDSolve[{
>     ph1''[t] + ph1'[t] + Sin[ph1[t]] - mu[t] - mu'[t] == 0.005,
>     ph2''[t] + ph2'[t] + Sin[ph2[t]] + mu[t] + mu'[t] == 0.005,
>     0.2 mu'[t] + mu[t] == ph1'[t] - ph2'[t], ph2 == 0, ph1 == 0,
>     ph2' == 0, ph1' == 0, mu == 0},
>    {ph1[t], ph2[t], mu[t]},
>    {t, 0, 100}];
>
> Plot[Evaluate[Tooltip[#, ToString[#]] & /@
>     {ph1[t], ph2[t], mu[t]} /. s],
>  {t, 0, 10},
>  Frame -> True, Axes -> False]
>
>
> Bob Hanlon
>
>
> On Thu, Dec 6, 2012 at 4:58 AM,  <hazem.abdelhafiz at gmail.com> wrote:
> > Dear all,
> > I want to solve this system of equations but I always get an error
> >
> > NDSolve::ndnum:Encountered non-numerical value for a derivative at t==0
> >
> > can any one help me on this
> >
> > s=NDSolve[{
> > ph1''[t]+ph1'[t]+sin[ph1[t]]-mu[t]-mu'[t]==0.005,
> > ph2''[t]+ph2'[t]+sin[ph2[t]]+mu[t]+mu'[t]==0.005,
> > 0.2mu'[t]+mu[t]==ph1'[t]-ph2'[t],
> > ph2==0,
> > ph1==0,
> > ph2'==0,
> > ph1'==0,
> > mu==0
> > },
> > {ph1[t],ph2[t],mu[t]},
> > {t,0,5000}
> > ]
> >