Evaluate a trigonometric value using period as an aide - Online Math Teacher

The video tutorial explains how to evaluate the cosine of angles greater than 2π by simplifying them using the unit circle. It demonstrates breaking down angles into thirds and highlights the redundancy of 2π in calculations. The tutorial walks through calculating the cosine of 2π/3, emphasizing the reflection about the Y-axis and the resulting negative value. The key takeaway is understanding how to factor out 2π to simplify angle evaluations.

How does the reflection about the Y-axis affect the cosine value?

What does it mean when the cosine of an angle is negative?