Answer:
[tex] cos^{-1}(cos\frac{ 7π}{6})=cos^{-1}(cos\frac{7*180}{6})[/tex]
[tex] cos^{-1}(cos{210})[/tex]
[tex] cos^{-}(cos(180+30))[/tex]
[since in third quadrant cos 30=-[tex] \frac{\sqrt{3}}{2}][/tex]
[tex] cos^{-}(- \frac{\sqrt{3}}{2})[/tex]
:150°or [tex] \frac{5π}{6}[/tex]
150°or [tex] \frac{5π}{6}[/tex]is a required answer.
