## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$1.77$
In order to get the answer in radians, we want to set the calculator in radians mode, and use the inverse cosine function (round off the result to two decimal places) to obtain: $\cos^{-1} (-0.2) =1.7722 \approx 1.77$