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Question

Question: If f (x) = log (log x), then f ' (x) at x = e is equal to –...

If f (x) = log (log x), then f ' (x) at x = e is equal to –

A

e

B

– e

C

e2

D

e–1

Answer

e–1

Explanation

Solution

f ' (x) = 1logx\frac{1}{\log x}× 1x\frac{1}{x}

f ' (5) = 1loge\frac{1}{\log e}× 1e\frac{1}{e} = e–1