## Trigonometry (11th Edition) Clone

$\sec^{-1}0$ is not defined.
Inverse Secant Function: $y=\sec^{-1}x$ or $y=$ arcsec $x$ means that $x=\sec y$, for $0 \leq y \leq \pi, y\displaystyle \neq\frac{\pi}{2}$. ---------------- The secant function is reciprocal to the cosine. There is no y from the interval $0 \leq y \leq \pi, y\displaystyle \neq\frac{\pi}{2}$ such that $\displaystyle \sec y=\frac{1}{\cos y}=0$ (the reciprocal of 0 does not exist) So, $\sec^{-1}0$ is not defined.