If $y = (\log x)^{\log x}, x > 1$ then $\frac{dy}{dx}$ is equal to |
$\log x \left[\frac{1 + \log(\log x)}{x}\right], x > 1$ $(\log x)^{\log x} \left[\frac{1 + \log x}{x}\right], x > 1$ $(\log x)^{\log x} \left[\frac{x + \log(\log x)}{x}\right], x > 1$ $(\log x)^{\log x} \left[\frac{1 + \log(\log x)}{x}\right], x > 1$ |
$(\log x)^{\log x} \left[\frac{1 + \log(\log x)}{x}\right], x > 1$ |
The correct answer is Option (4) → $(\log x)^{\log x} \left[\frac{1 + \log(\log x)}{x}\right], x > 1$ Let $u=\log x$ so $y=u^{\,u}$. $\log y = u\log u$ Differentiate w.r.t. $x$: $\frac{1}{y}\frac{dy}{dx} = \frac{du}{dx}\big(\log u + 1\big)$ Since $\frac{du}{dx}=\frac{1}{x}$, $\frac{dy}{dx} = y\cdot \frac{1}{x}\big(\log u + 1\big)$ Back-substitute $y=u^{u}$ and $u=\log x$: $\displaystyle \frac{dy}{dx} = (\log x)^{\log x}\,\frac{1+\log(\log x)}{x}$ |