ASKSAGE: Sage Q&A Forum - Latest question feedhttps://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Fri, 24 Oct 2014 10:16:29 -05002nd-order ODE: Maxima wants sign of 1 constant before finishinghttps://ask.sagemath.org/question/24624/2nd-order-ode-maxima-wants-sign-of-1-constant-before-finishing/ I'm trying to solve a 2nd-order nonlinear ODE using desolve(). Maxima gets partway through, but then asks for the sign of one of the integration constants. How can I tell it to assume something that doesn't exist before I call desolve()?
t,P,x0=var('t,P,x0')
x=function('x',t)
de=(diff(x,t,2)*x^2+P==0)
forget()
assume(P>0,x0>0)
desolve(de,x,ics=[0,x0,0],ivar=t)
gives the error:
TypeError: ECL says: Maxima asks: Is %k1 positive or negative?
Hoss N. FefferFri, 24 Oct 2014 10:16:29 -0500https://ask.sagemath.org/question/24624/Difficulty solving some second order differential equationshttps://ask.sagemath.org/question/10177/difficulty-solving-some-second-order-differential-equations/I have trouble finding 10% and 90% of the rise time in a second order differential equation.
I have tried to search but i have not solved my issue, so now i ask here.
I have added the code to aleph.sagemath.org however the link is crazy long so i put it in a short link: [http://bit.utoft.org/138hfAz](http://bit.utoft.org/138hfAz)
The code is also on pastebin
[http://pastebin.com/4hwdLJuT](http://pastebin.com/4hwdLJuT)
Please help :)
Cheers
J. UtoftjesperFri, 31 May 2013 06:51:05 -0500https://ask.sagemath.org/question/10177/