It is given that, \(y=\operatorname{cosec}^{-1} x\)
\(\text {and } \frac{d y}{d x}=\frac{-1}{|x| \sqrt{x^2-1}}\)
\(\because\) Domain of \(\operatorname{cosec}^{-1} x\) is \(\left[-\frac{\pi}{2}, \frac{\pi}{2}\right]-\{0\}\) and the \(\frac{d y}{d x}\) is define for \(x \in\left(-\frac{\pi}{2}, 0\right) \cup\left(0, \frac{\pi}{2}\right)\). Because for derivatives we should exclude the end points of a internal.
Hence, option (c) is correct.