scott wrote:

> You can write an exact differential equation for the motion of a 
> pendulum, but it will have a sin or cos in it because the string/rod is 
> at an angle to gravity.  Usually you replace sin(x) with just x to make 
> it easy to solve and get a simple solution.  x (in radians!) is actually 
> a pretty good approximation to sin(x) for angles up to 10 or 20 degrees 
> - try it. Obviously the bigger swings your pendulum makes, the more 
> inaccurate the "simple" equation will be.

Damn. And I thought it was an "exact" equation. Oh well...

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