Find the principal value of: `sin^(-1)(-1/2)`

Explanation

Let `sin^(-1)(-1/2)=y`

`sin y=-1/2=-sin frac{pi}{6}=sin(-pi/6)`

We know that the range of the principal value of `sin^(-1) x` is `[-pi/2, pi/2]` and `sin(-pi/6)=-1/2`