Write the principal value of, `cos^(-1)\ (cos(7pi)/6)`

Explanation

Here, we will use `cos(pi+x) = cos(pi-x)`

`:. cos((7pi)/6) = cos(pi+pi/6) = cos(pi-pi/6)`

`= cos((5pi)/6)`

`:. cos^-1(cos((7pi)/6)) = cos^-1(cos((5pi)/6))`

`=(5pi)/6`, which is the required principal value as it is between `0` and `pi`.