Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Continuity and Differentiability

Question:
Find the derivative of $(\log x)^{\log x},x>1$
Options:
$(1+\log(\log x)/x)$
$(\log x)^{\log x}(\frac{1+\log(\log x)}{x})$
$(\log x)^{\log x}$
$(\log x)^{1+\log x}$
Correct Answer:
$(\log x)^{\log x}(\frac{1+\log(\log x)}{x})$
Explanation:
Let $y=(\log x)^{\log x}$. Taking log in both sides we get $\log y=\log x\log(\log x)$. Differentiating both sides w.r.to x we get $1/y\frac{dy}{dx}=\frac{1+\log(\log x)}{x}$. Hence $\frac{dy}{dx}=y(\frac{1+\log(\log x)}{x})=(\log x)^{\log x}(\frac{1+\log(\log x)}{x})$