The function $\mathrm{y}={\sin }^{-1}\left(\mathrm{cosx}\right)$ is not differentiable at

$$\begin{gathered} \mathrm{y}={\sin }^{-1}\left(\cos \mathrm{x}\right) \\ \frac{\mathrm{dy}}{\mathrm{dx}}=\frac{1}{\sqrt{1-{\cos }^2\mathrm{x}}}\left(-\sin \mathrm{x}\right)=\frac{-\sin \mathrm{x}}{\left|\sin \mathrm{x}\right|} \end{gathered}$$

y is not differentiable if $\sin \mathrm{x}=0$

y is not differentiable if $\mathrm{x}=-2\mathrm{\pi }, \mathrm{\pi }, 2\mathrm{\pi }$

y is not differentiable if $\mathrm{x}=-2\mathrm{\pi }, \mathrm{\pi }, 2\mathrm{\pi }$