On Wed, Nov 11, 2009 at 1:19 PM, Jaasiel Ornelas <[email protected]> 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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