Evaluating for cosine using coterminal angles

The video tutorial explains how to evaluate trigonometric functions using the smallest positive or negative coterminal angles. It demonstrates the process of finding coterminal angles by adding or subtracting 2π, and simplifies the angle -9π/4 to -π/4. The tutorial further explains how to evaluate the cosine of the simplified angle, considering the coordinate points and quadrants involved.

What is the relationship between 2π and the fractions 4π/2 and 8π/4, and how does this affect the addition of coterminal angles?

When evaluating cosine for -π/4, what coordinate point do you use, and how does the quadrant affect the sign of the values?