# Asymptotic behavior of two functions

I have trouble figuring out the asymptotic behavior of two functions.

1. If $f(n) = n \log n$, then what do we know about $f^{-1}(n)$? I.e. what is the asymptotic behavior of $g(n)$ such that $g(n) \log(g(n)) = \Theta(n)$, perhaps in terms of some familiar functions?

2. Behavior of $n^{\frac{1}{\log \log n}}$. I know that $n^{\frac{1}{\log n}} = e$, so this function would be super-constant. But what is known about its asymptotic behavior?

• By asymptotic behavior, do you want to find a function that is ~ to $f$? – Gregory Grant Feb 8 '16 at 21:39
• $n^{\frac{1}{\ln(n)}} = e$ if and only if $n > 0$, actually. Anyway, you can always try some technique like the approximation $$\ln(n!) \approx n\ln(n) - n$$ and manipulate to see if you can pull out the rabbit! – Von Neumann Feb 8 '16 at 21:41
• @GregoryGrant Yes, or if that is too strict then possible upper and lower bounds. – taninamdar Feb 8 '16 at 21:48