Answer
$\tanh z$
Work Step by Step
Since, $\dfrac{d}{dx} (\cosh x)=\sinh x$
As we are given that $y=\ln (\cosh z)$
Then, on differentiating, we have:
$\dfrac{dy}{dz}= (\sinh z) \dfrac{1}{\cosh z} =\tanh z$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.