How to evaluate the difference of two angles for cosine function

The video tutorial explains the use of the cosine difference formula, focusing on evaluating trigonometric functions for specific angles. It covers the understanding of coordinate points on the unit circle and the process of simplifying trigonometric expressions. The tutorial emphasizes the importance of simplification for achieving full credit in exams.

Explain how to simplify the expression obtained from evaluating the cosine and sine for the given angles.

What is the significance of finding common denominators when simplifying trigonometric expressions?