Answer
$2 \cosh {\dfrac{x}{3}}$
Work Step by Step
Since, $\dfrac{d}{dx} (\sinh x)=\cosh x$
As we are given that $y=6 \sinh {\dfrac{x}{3}}$
Then, on differentiating , we have
$\dfrac{dy}{dx}=6 \cosh {\dfrac{x}{3}} (\dfrac{1}{3})=2 \cosh {\dfrac{x}{3}}$
