# Derivative of ln(ln x)

by Physicsnut
Tags: derivative, lnln
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 P: 1 1. The problem statement, all variables and given/known data Differentiate $$ln(lnx)$$ 2. Relevant equations 3. The attempt at a solution My solution: Let $f(x)=lnx$, since${d/dx}ln f(x)={f'(x)/f(x)}$, ${d/dx}ln(lnx)={{1/x}/lnx}/times {1/x} ={1/x^2lnx}$.
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Hi Physicsnut! Welcome to PF!
 Quote by Physicsnut Let f(x)=lnx, since d/dx ln f(x) = {f'(x)/f(x)},
yes
 {d/dx}ln(lnx) = {{1/x}/lnx}/times {1/x}
nooo
 Emeritus Sci Advisor PF Gold P: 9,355 Surround your LaTeX code with either ## or $$. A single  doesn't work. This is deliberate, because it would have confused people who don't use LaTeX but write stuff about money. LaTeX guide for the forum.  Math Emeritus Sci Advisor Thanks PF Gold P: 39,497 Derivative of ln(ln x) ##e^x##$$x^n $\int f(x)dx$ $$\frac{df}{dx}$$ Wow! All this time I have been using "itex" and "tex"!
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 Quote by HallsofIvy Wow! All this time I have been using "itex" and "tex"!
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