## Calculus (3rd Edition)

$\frac{2}{x} \ln x$
$y= (\ln x)^{2}$ Let us substitute $t= \ln x$ Then, $y= t^{2}$ According to the chain rule, $\frac{dy}{dx}=\frac{dy}{dt}\cdot\frac{dt}{dx}= 2t\times\frac{1}{x}$ Undoing substitution, we obtain $\frac{dy}{dx}= \frac{2}{x} \ln x$