Here is Jamie's work.
cos ¹(cos(x))
x ~ 1.65 + 2πη
Using cos(x) = cos(x + 2π)
x...-4.63, 1.65, 7.93...
=
x ≈
cos ¹(-0.08)
1.65
Using cos(x) = cos(π - x)
and cos(x) = cos(x + 2)
* ~ 1.49 + 2πη
x...-4.79, 1.49, 7.77...
The solutions to x in the interval from - to π are x 1.49 and ≈ 1.65.