Post Reply 
solving diff. equations on Prime vs 50g and 48G ?
03-09-2023, 12:36 PM (This post was last modified: 03-09-2023 01:26 PM by OlidaBel.)
Post: #1
solving diff. equations on Prime vs 50g and 48G ?
Hi,
In this 50G tutorial is explained how to solve differential equations with iterations : it's intuitive and can be done on the 48GX as well.
https://www.ele.uri.edu/faculty/vetter/O...ations.pdf

It's computed numerically(kind of Runge Kutta?) step by step in a convenient way and it is said : "The most convenient way to numerically solve a differential equation is the built-in numeric differential equation
solver and its input form
" See last pages of this URL.
The Example 2 is interesting : "A physical body moves under the influence of a constant force F in a viscous liquid. The differential equation of its
motion is"
etc.

I wonder how this way of computing can be done on the HP Prime, numerically, step by step.

Eddie has proposed a way to "mimics" DE numerical solving, in a creative way, inside the Geometry app :
http://edspi31415.blogspot.com/2015/11/h...art-5.html

Any idea ?

PS: I don't want here play with a symbolic CAS solution ;-)
thanks,

---
HP 48GX, Prime G2, 50G, 28S, 15c CE. SwissMicros DM42, DM15L
A long time ago : 11C, 15C, 28C.
Find all posts by this user
Quote this message in a reply
03-09-2023, 07:24 PM
Post: #2
RE: solving diff. equations on Prime vs 50g and 48G ?
This:

Syntax:
odesolve(Expr, VectVar, VectInit, FinalVal, [tstep=Val, curve])

Ordinary Differential Equation solver

Solves an ordinary differential equation given by Expr, with variables declared in VectVar and initial conditions for those variables declared in VectInit. For example, odesolve(f(t,y),[t,y],[t0,y0],t1) returns the approximate solution of y'=f(t,y) for the variables t and y with initial conditions t=t0 and y=y0.


Example:
odesolve(sin(t*y),[t,y],[0,1],2) → [1.82241255674]

may be what you want.

-road
Find all posts by this user
Quote this message in a reply
03-10-2023, 11:06 AM
Post: #3
RE: solving diff. equations on Prime vs 50g and 48G ?
(03-09-2023 07:24 PM)roadrunner Wrote:  Example:
odesolve(sin(t*y),[t,y],[0,1],2) → [1.82241255674]
Thanks Roadrunner.

---
HP 48GX, Prime G2, 50G, 28S, 15c CE. SwissMicros DM42, DM15L
A long time ago : 11C, 15C, 28C.
Find all posts by this user
Quote this message in a reply
03-12-2023, 05:31 PM
Post: #4
RE: solving diff. equations on Prime vs 50g and 48G ?
If you want the intermediate steps, add curve as last optional argument
odesolve(sin(t*y),[t,y],[0,1],2,curve)
Should also work for differential systems.
Find all posts by this user
Quote this message in a reply
03-13-2023, 01:20 PM
Post: #5
RE: solving diff. equations on Prime vs 50g and 48G ?
(03-12-2023 05:31 PM)parisse Wrote:  If you want the intermediate steps, add curve as last optional argument
odesolve(sin(t*y),[t,y],[0,1],2,curve)
Should also work for differential systems.

ah oui, indeed. Merci M. Parisse !
Strange, t had a value here, and with the equation above, it gives an error; I was forced to "purge" t in order to make it working.

---
HP 48GX, Prime G2, 50G, 28S, 15c CE. SwissMicros DM42, DM15L
A long time ago : 11C, 15C, 28C.
Find all posts by this user
Quote this message in a reply
10-13-2023, 12:38 AM
Post: #6
RE: solving diff. equations on Prime vs 50g and 48G ?
Can I use odesolve to solve a system of differential equations numerically? I know that you can plot the solution (or at least the phase plane) like the example included in the help of the function.
Find all posts by this user
Quote this message in a reply
10-13-2023, 06:31 AM
Post: #7
RE: solving diff. equations on Prime vs 50g and 48G ?
Xcas online help has an example
odesolve(0..pi,(t,v)->{[-v[1],v[0]]},[0,1])
Needs to be modified for the Prime since {} does not have the same meaning. I would try with BEGIN ... END instead.
Find all posts by this user
Quote this message in a reply
Post Reply 




User(s) browsing this thread: 1 Guest(s)