Skip to main contentSkip to solution

The derivative of (log⁡x)x(\log x)^x with respect to log⁡x\log x is

Solution

✅ Correct Option: 3

The derivative of (log⁡x)x(\log x)^x with respect to log⁡x\log x needs to be found.

This requires differentiating with respect to (log⁡x)(\log x), not with respect to xx.


Using the chain rule:

dd(log⁡x)=ddx×dxd(log⁡x)\frac{d}{d(\log x)} = \frac{d}{dx} \times \frac{dx}{d(\log x)}

Since d(log⁡x)dx=1x\frac{d(\log x)}{dx} = \frac{1}{x}, we have:

dxd(log⁡x)=x\frac{dx}{d(\log x)} = x


Let y=(log⁡x)xy = (\log x)^x

Taking the natural logarithm of both sides:

ln⁡y=x⋅ln⁡(log⁡x)\ln y = x \cdot \ln(\log x)

Differentiating both sides with respect to xx:

1y⋅dydx=ln⁡(log⁡x)+x⋅1log⁡x⋅1x\frac{1}{y} \cdot \frac{dy}{dx} = \ln(\log x) + x \cdot \frac{1}{\log x} \cdot \frac{1}{x}

1y⋅dydx=ln⁡(log⁡x)+1log⁡x\frac{1}{y} \cdot \frac{dy}{dx} = \ln(\log x) + \frac{1}{\log x}


Solving for dydx\frac{dy}{dx}:

dydx=y[ln⁡(log⁡x)+1log⁡x]\frac{dy}{dx} = y\left[\ln(\log x) + \frac{1}{\log x}\right]

dydx=(log⁡x)x[1+log⁡x⋅ln⁡(log⁡x)log⁡x]\frac{dy}{dx} = (\log x)^x\left[\frac{1 + \log x \cdot \ln(\log x)}{\log x}\right]


Converting to the derivative with respect to log⁡x\log x:

dyd(log⁡x)=dydx×dxd(log⁡x)\frac{dy}{d(\log x)} = \frac{dy}{dx} \times \frac{dx}{d(\log x)}

dyd(log⁡x)=(log⁡x)x[1+log⁡x⋅ln⁡(log⁡x)log⁡x]×x\frac{dy}{d(\log x)} = (\log x)^x\left[\frac{1 + \log x \cdot \ln(\log x)}{\log x}\right] \times x

dyd(log⁡x)=x⋅(log⁡x)x−1[1+log⁡x⋅ln⁡(log⁡x)]\frac{dy}{d(\log x)} = x \cdot (\log x)^{x-1}[1 + \log x \cdot \ln(\log x)]


Therefore, the answer is:

x(log⁡x)x−1[1+log⁡x⋅ln⁡(log⁡x)]x(\log x)^{x-1}[1 + \log x \cdot \ln(\log x)]

Keyboard Shortcuts

  • Left arrow: Previous question
  • Right arrow: Next question
  • S key: Jump to solution
  • Q key: Jump to question