If $y^{x}=x^{y}$, then $\frac{d y}{d x}$ is :
Answer & explanation
Correct answer: option 2
$y^x=x^y \Rightarrow \log y^x=\log x^y$
$\Rightarrow x \log y=y \log x$
$\Rightarrow x . \frac{1}{y} \frac{d y}{d x}+\log y . 1=y . \frac{1}{x}+\log x . \frac{d y}{d x}$
$\Rightarrow\left(\frac{x}{y}-\log x\right) \frac{d y}{d x}=\frac{y}{x}-\log y$
Hence (2) is correct answer ⇒ $\frac{d y}{d x}=\frac{y(y-x \log y)}{x(x-y \log x)}$