Algebra-2

Question Analysis
This problem assesses the ability to evaluate the cosine function at specific angles using the unit circle.

Key Concept Explanation
The cosine function, , can be evaluated using the unit circle. The angle corresponds to a point in the third quadrant where the x-coordinate (cosine value) is negative.

Step-by-step Solution
1. Identify the reference angle for , which is .
2. In the third quadrant, the cosine value is negative.
3. The cosine of the reference angle is

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