MATLAB Answers

## How to solve this system of non linear equations ?

Asked by Marin Lallemand

### Marin Lallemand (view profile)

on 22 Oct 2018
Latest activity Commented on by Marin Lallemand

### Marin Lallemand (view profile)

on 22 Oct 2018
Hello everyone !
I'm working on a study concerning "trajectory équations", but i have a problem to solve these équations with Matlab. The system is :
d(Vx)/dt = - C * sqrt(Vx^2 + Vy^2 + Vz^2) * Vx
d(Vy)/dt = - C * sqrt(Vx^2 + Vy^2 + Vz^2) * Vy
d(Vz)/dt = - g - C * sqrt(Vx^2 + Vy^2 + Vz^2) * Vz
I have used the functions ode45 and ode23s, but i dont find the good results, so i dont know if my problem comes from my équations or the code...
Is someone know how to solve this system with Matlab ?
Thank you in advance !
Marin

John D'Errico

### John D'Errico (view profile)

on 22 Oct 2018
So show your code, instead of asking someone to completely write new code for you. Tell people what values the constants C and g take on. What initial values apply. Over what range of t are you looking to solve the problem.
Tell people why you think the results are not good.
Marin Lallemand

### Marin Lallemand (view profile)

on 22 Oct 2018
In fact, I cant show my code beacuse it is confidential. I dont ask for a new code, i want to write it by myself. I juste want to know if there is another method to solve this kind of system (coupled differential équations), because it seems that ode45 and ode23s dont work here.

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