Simplifying an expression using the sum of two angles for cosine

The video tutorial addresses the challenge of transitioning from numbers to variables in mathematical expressions. It emphasizes the importance of applying known processes to new problems, specifically focusing on simplifying expressions using the cosine of a sum formula. The instructor guides students through labeling variables, substituting values, and evaluating expressions using the unit circle. The tutorial concludes with a setup for a problem, reinforcing the learned concepts.

What new insight or understanding did you gain from this video?