i am trying to solve this ode but can't seem to get any traction:

$\displaystyle \frac {d^2 \theta(\tau)} {d \tau^2} + \sin(\theta(\tau) ) = 0$

$\displaystyle \theta(0) = A$

$\displaystyle \dot{\theta}(0) = 0$

How would i go about solving this?

Thank you very much!!

MT

(This is a derivitive of a nasty case where: $\displaystyle \frac {d^2 \theta(\tau)} {d \tau^2} + \sin(\theta_{s} + \theta(\tau) ) = 0$ which I still don't know how to solve with the same B.C)