Evaluate cosine sum and difference identity given as expression

The video tutorial explains how to calculate the cosine of specific angles, such as 31 and 1 degrees, by recognizing and applying a formula for the cosine of angle differences. The instructor guides students through the process of combining angles within the cosine function and clarifies the operations involved. The tutorial concludes with a review of the steps and a final clarification to ensure understanding.

What is the significance of recognizing the cosine formula written on the board?

How do you calculate the cosine of 30 degrees?