Using addition of two angles with triangles to evaluate for cosine

The video tutorial explains how to solve a trigonometry problem involving the evaluation of sine and cosine values for angles in different quadrants. The instructor guides through constructing triangles, applying the Pythagorean theorem, and using the cosine of sum formula to find the solution. The process includes detailed calculations and simplification of results, emphasizing the importance of understanding quadrant positions and reducing fractions.

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