If $y=\log (\cosh x)$ then $\frac{d^2 y}{d x^2}=$

Question

Aicharya · Accepted Answer

$y=\log (\cos \mathrm{h} x)$ Differentiating w.r.t. ' $x$ ' on both sides $ \begin{aligned} & \frac{d y}{d x}=\frac{1}{\cosh x}(\sinh x) \ & \frac{d y}{d x}=	anh x \end{aligned} $ Again differentiating w.r.t. ' $x$ ' on both sides $ \frac{d^2 y}{d x^2}=\operatorname{sech}^2 x $ Hence, option (1) is correct

If $y=\log (\cosh x)$ then $\frac{d^2 y}{d x^2}=$

Solution