Derivatives · Review Exercise 109

With the aid of a graphing utility, explain why the function is not differentiable everywhere on its domain. Specify the points where the function is not differentiable.

Given that the volume of a right circular cone is $V=\frac{1}{3}\pi r^{2}h$ and that a given cone has a fixed height of 9 cm and variable radius length, find the instantaneous rate of change of volume with respect to radius length when the radius is 2 cm. Give an exact answer in terms of $\pi$

Its source prints no answer for this problem, so there's nothing to check against.

OpenStax, Precalculus 2e · §12.4 Derivatives · Review Exercise 109