Evaluate the arc cosine without a calculator

The video tutorial explains how to find the angle whose cosine is -1/2 using the unit circle. It identifies the coordinate points on the unit circle where the cosine is -1/2 and determines the angles corresponding to these points. The tutorial also discusses the restrictions on cosine values and concludes with the correct angle within the specified range.

What is the cosine value we are trying to find the angle for?

• 1/2

• -1/2

• 0

• -1

Which of the following is a coordinate point on the unit circle where the cosine is -1/2?

• (-1/2, -sqrt(3)/2)

• (1/2, -sqrt(3)/2)

• (-1/2, sqrt(3)/2)

• (1/2, sqrt(3)/2)

What are the angles on the unit circle that correspond to a cosine of -1/2?

• π/3 and 2π/3

• 2π/3 and 4π/3

• π/4 and 3π/4

• π/6 and 5π/6

What is the range of angles for which cosine is restricted?

• π/2 to 3π/2

• 0 to π

• π to 2π

• 0 to 2π

What is the correct angle between 0 and π where the cosine is -1/2?

• 4π/3

• 2π/3

• 5π/3

• π/3