# Homework Help: Second order differential equation Lagrange mechanics

1. Jan 16, 2010

### player1_1_1

1. The problem statement, all variables and given/known data
from one thing in Lagrange mechanics (general coordinates: $$\phi,\dot\phi,s,\dot{s}$$) I got a equation system:
$$\begin{cases}R\ddot\phi\sin\phi+R\dot\phi^2\cos\phi+\ddot{s}=0\\ g\sin\phi+R\ddot\phi+\ddot{s}\sin\phi=0\end{cases}$$
3. The attempt at a solution
Is it good idea to make a thing which is approximating a equations for little $$\phi$$ and do it like this $$\sin\phi\approx\phi,\quad\cos\phi\approx1$$?