Chapter 1.7, Problem 16ES

Use a calculating utility to approximate the solution of each equation. Where radians are used, express your answer to four decimal places, and where degrees are used, express it to the nearest tenth of a degree. [Note: In each part, the solution is not in the range of the relevant inverse trigonometric function.]

(a) $\cos x=-0.85,\pi <x<3\pi /2$

(b) $\cos \theta =0.23,-90°<\theta <0°$