Differentiation Question 458

Question: If $ y={x^{(x^{x})}} $ , then $ \frac{dy}{dx}= $

[AISSE 1989]

Options:

A) $ y[x^{x}(\log ex).\log x+x^{x}] $

B) $ y[x^{x}(\log ex).\log x+x] $

C) $ y[x^{x}(\log ex).\log x+{x^{x-1}}] $

D) $ y[x^{x}({\log _{e}}x).\log x+{x^{x-1}}] $

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Answer:

Correct Answer: C

Solution:

$ y={x^{(x^{x})}}\Rightarrow \log y=x^{x}\log x $

Therefore $ \frac{1}{y}\frac{dy}{dx}=\frac{dz}{dx}.\log x+\frac{1}{x}.z $ , (where $ x^{x}=z $ )
$ \Rightarrow \frac{dy}{dx}={x^{(x^{x})}}[ x^{x}(\log ex).\log x+{x^{x-1}} ] $ , $ { \because \frac{dz}{dx}=x^{x}\log ex } $ .