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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Mathematics
Chapter
Differentiation

NTA Abhyas 2020 · Mathematics · Differentiation

Consider a function& f (x) = x^ x , x ∈ [1, ∞). If g (x) is the...

Consider a function& f \left(x\right) = x^{x}, \forall x \in \left[1,\infty\right). If g(x)g \left(x\right) is the inverse function of f(x)f \left(x\right), then the value of g′(4)g^{′} \left(4\right) is equal to

Options

  1. Alog⁡2e\log_{2} e
  2. B12log⁡2ee\dfrac{1}{2}\log_{2e} e
  3. C14log⁡2ee\dfrac{1}{4}\log_{2e} e
  4. D12log⁡e2e\dfrac{1}{2}\log_{\mathrm{e}} 2e

Correct answer

C. 14log⁡2ee\dfrac{1}{4}\log_{2e} e

Step-by-step solution

f(x)=xx⇒logf(x)=xlogxf\left(x\right) = x^{x} ⇒ log f\left(x\right) = xlog x
Differentiating with respect to xx, we get,

f′f^{′}\left(x\right) = x^{x} (1+log⁡x)\left(1 + \log x\right)
Now, by property g′(f(x))=1f′(x)∵g(x) is  the  inverse  of f(x)g^{′} \left(f \left(x\right)\right) = \dfrac{1}{f^{′} \left(x\right)} {∵ g\left(x\right)\text{ is }\text{ the }\text{ inverse }\text{ of } f \left(x\right)}<br/>Putting<br />Puttingx = 2<br/><br />g^{'}\left(f\left(2\right)\right) = \dfrac{1}{f^{'}\left(2\right)}⇒ g^{'} \left(4\right) =\dfrac{1}{{2}^{2} \left(1 + \log 2\r right)}=\dfrac{1}{4}\left(\log_{2e} e\right)</p></p>

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