Solving coupled ODEs via ode45

Hello,

I have 2 secound order and coupled ordinary differential equations. For the first equation, I could find an explicit solution, i.e. d^2y/dt^2=.....

However, for the second equation, I could not find an explicit solution. Therefore, I couldn't use ode45 etc. How can I solve these equations numerically?

Thank you in advance

[Torsten]

If you don't know the equation, how do you want to solve it ? Or what do you mean by

However, for the second equation, I could not find an explicit solution. Therefore, I couldn't use ode45 etc.

[Seymen]

I didn't say I don't know the equation. What I meant was that I cannot put the equation into this form: d^2y/dt^2=.....

[Torsten]

ode45 can solve first-order initial value problems. Thus your equations must be of the form dy/dt = f(t,y).

If you have a second-order differential equation

d^2y/dt^2 = g(t,y,dy/dt)

, it can be written as two first-order differential equations by putting

z(1) = y, z(2) = dy/dt

The system then reads

dz(1)/dt = z(2)
dz(2)/dt = g(t,z(1),z(2))

[Steven Lord]

Can you show us the form of the differential equations that you do know? If you show us the mathematical equations we may be able to help you translate them into MATLAB code.

Answer 1

[Sulaymon Eshkabilov]

If your equation is implicit then, ode15i might be the tool to use.

https://www.mathworks.com/help/matlab/ref/ode15i.html