Find the principal values of `cos^(-1)((sqrt(3))/2)` and `cos^(-1)(-1/2)`

Explanation

`cos y=frac{sqrt 3}{2}=cos frac{pi}{6}`

The principle value of `cos ^(-1) frac{sqrt 3}{2}` is `pi/6`

`cos^(-1)(-1/2)=(2pi)/3`