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 is the formula for the cosine of the sum of two angles?

• cos(U + V) = cos(U) * cos(V) + sin(U) * sin(V)

• cos(U + V) = cos(U) * cos(V) - sin(U) * sin(V)

• cos(U + V) = sin(U) * sin(V) + cos(U) * cos(V)

• cos(U + V) = sin(U) * cos(V) - cos(U) * sin(V)

When applying the cosine sum formula to X and π/6, what is the first step?

• Multiply cos(X) by cos(π/6)

• Add sin(X) to cos(π/6)

• Subtract sin(X) from sin(π/6)

• Multiply cos(X) by sin(π/6)

Why is it important to distribute negative signs correctly in expressions?

• To avoid changing the value of the expression

• To make the expression more complex

• To ensure the expression remains positive

• To simplify the expression

What common mistake do students make when dealing with expressions involving subtraction?

• Multiplying instead of adding

• Failing to distribute the negative sign

• Not using the correct formula

• Forgetting to add terms

What is the value of sine(π/6)?

• 0

• 1

• √3/2

• 1/2

What angle corresponds to a Y-coordinate of -1 on the unit circle?

• π/2

• 3π/2

• π

• 2π

In the context of the unit circle, what is the significance of the angle 3π/2?

• It is where the X-coordinate is -1

• It is where the Y-coordinate is -1

• It is where the Y-coordinate is 0

• It is where the X-coordinate is 1