I'm using:
Sage Version 4.1.1, Release Date: 2009-08-14
We just started laplace in my class, so I did not know that laplace
transforms don't solve non linear ode's. Sorry :p
On Nov 11, 12:01 pm, David Joyner <wdjoy...@gmail.com> wrote:
> On Wed, Nov 11, 2009 at 1:19 PM, Jaasiel Ornelas <jrodri1...@gmail.com> wrote:
>
> > I can't get desolve_laplace to give me a good output. I had already
> > tried the regular solve (desolve) and it gave to told me that it
> > cannot solve that equation. This is my code:
>
> > sage: (g,t) = var('g,t')
>
> > sage: y=function('y',t)
>
> > sage: DEiii = pi * (39/100*y + 1/2)^2* diff(y,t) + a * sqrt(2*g*y)
>
> This is a non-linear ODE. You can't use Laplace transforms
> to solve such ODEs.
>
> However, it is separable and I can solve a slightly simpler version:
>
> sage: t = var("t")
> sage: y = function("y",t)
> sage: DE = y^2*diff(y,t)+sqrt(y)==0
> sage: desolve(DE,[y,t])
> -2/5*y(t)^(5/2) == c + t
>
> Which version of Sage are you using?
>
>
>
> > sage: a = .5^2*pi
>
> > sage: DEiii
>
> > 1/10000*(39*y(t) + 50)^2*pi*D[0](y)(t) + 0.250000000000000*pi*sqrt(g*y
> > (t))*sqrt(2)
>
> > sage: desolve(DEiii, [y,t])
> > Traceback (most recent call last):
> > ...
> > NotImplementedError: Maxima was unable to solve this system.
>
> > sage: desolve_laplace(DEiii, ["t","y"], [0,50,0])
> > "?%ilt(-(1521*'laplace('y(t)^2*'diff('y(t),t,1),t,false)+3900*'laplace
> > ('y(t)*'diff('y(t),t,1),t,false)+2500*sqrt(2)*'laplace(sqrt(g*'y
> > (t)),t,false)-125000)/(2500*false),false,t)"
>
> > Perhaps it's because I can't understand the output, but if anyone
> > could help me with this, thank you.
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