Let $S$ be the set of points at which the function $f: \mathbb{R} \rightarrow \mathbb{R}$ defined by

Question

Let $S$ be the set of points at which the function $f: \mathbb{R} \rightarrow \mathbb{R}$ defined by $f(x)=|\cos x|$ is not differentiable. Then $|\mathrm{S}|$ is equal to

Professor PC Thomas Classes · Answer

$|\cos x|$ is non-differentiable where $\cos x = 0$, i.e., $x = (2n+1)\pi/2$.