1. differential equation

Hi!

The equation:

-sin(y) + sin(x) = y''

(of course y=y(x) and y'' means (d^2y)/(dx^2) )

I'm looking for solution (elliptical integral maybe?), or at least an advice how to solve this.
The numerical solution (runge kutta or something) with Mathematica or Mathlab will also be very good.
I just have no idea how to solve this, and if anyone has done something similar, please advice!!!

Thanks

2. Well, y=x is an obvious solution, but for a more general one (or less trivial) I really don't know how to attack this. To give you an idea you could try this

3. Originally Posted by henry25
Hi!

The equation:

-sin(y) + sin(x) = y''

(of course y=y(x) and y'' means (d^2y)/(dx^2) )

I'm looking for solution (elliptical integral maybe?), or at least an advice how to solve this.
The numerical solution (runge kutta or something) with Mathematica or Mathlab will also be very good.
I just have no idea how to solve this, and if anyone has done something similar, please advice!!!

Thanks
What is the context (how has this equation arisen)? Looks like an undamped forced pendulum to me.

Numerical solution (at least for a duration that is not too long) is trivial but will require initial conditions.

CB

4. Yes, it is compound pendulum.
The pendulum is forced to fluctuate by momentum, that looks like Asin(t*omega)
I put x for the time and y for angle.

So initial conditions can be: y(0)=0 and y'(0)=0.