How to solve this system of non linear equations ?

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]

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]

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.