Simplify an expression using the sum and difference formulas

The video tutorial explores recognizing patterns in trigonometric expressions, specifically focusing on the sine and cosine functions. It discusses applying the sum and difference formulas to these expressions and demonstrates how to simplify them further. The tutorial concludes with additional notes and remarks.

Can you explain how to apply the sum and difference formula to the expression X + Y?

What simplification can be made from the expression sqrt(9 - 4)?