Evaluate arcsec sec -9pie/7
pleas explain the steps thanks
you need to know that the range of the inverse secant function is ...
$\displaystyle \left[0,\frac{\pi}{2}\right) \cup \left(\frac{\pi}{2} , \pi\right]
$
get an angle co-terminal with $\displaystyle \theta = -\frac{9\pi}{7}$ that is in the range of the inverse secant function ...
$\displaystyle \sec\left(-\frac{9\pi}{7}\right) = \sec\left(\frac{5\pi}{7}\right)$
$\displaystyle arcsec\left[\sec\left(\frac{5\pi}{7}\right)\right] = \frac{5\pi}{7}$