What is the principal value cost of cos -1

(0.69)

We are asked to find the principal value of

cos ⁻¹ (0.69)

which is just the least positive angle

cos ⁻¹ (0.69) = 46.37°

Other values of

cos ⁻¹ (0.69) is

46.37° - 180° n

where n is a whole number