How to solve a equation using difference of two angles

The video tutorial covers the cosine function, focusing on the formulas for the sum and difference of angles. The teacher explains how to apply these formulas to specific angles and expressions, emphasizing the importance of using the correct formulas. The tutorial also highlights common mistakes, such as failing to distribute negative signs, and demonstrates how to simplify expressions using the distributive property. The lesson concludes with solving for the sine of X using the unit circle, identifying the angle where the Y-coordinate is -1.

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