#### Answer

$y=0$

#### Work Step by Step

$y=\sec^{-1}x =$arcsec$x$
Domain: $(-\infty, -1]\cup[1, \infty)$
Range: $[0,\displaystyle \frac{\pi}{2})\cup(\frac{\pi}{2},\pi]$
Quadrants (unit circle): I and II
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$y$ is the number from $[0,\displaystyle \frac{\pi}{2})\cup(\frac{\pi}{2},\pi]$
such that $\sec y=1$
$(\cos y=1)$
$\cos 0=1$, that is,$ \sec 0=1, $
and
$0\displaystyle \in[0,\frac{\pi}{2})\cup(\frac{\pi}{2},\pi]$.
So,
$y=0$