Stirling's approximation

[Paradox]

I was wondering how Stirling's approximation

x! ~ sqrt(2[pi]x)xxe-x

was derived. Anyone know?

[Big Jeff]

This article (http://mathworld.wolfram.com/StirlingsApproximation.html) at Mathworld derives Stirling's approximation step by step. [:)]

[Paradox]

Thanks for the link, Jeff. It helped a lot [:)]