Question

When does cosine equal negative one-half?
a) π/3
b) 2π/3
c) 4π/3
d) 5π/3

Answer 1

To find where cosine equals -1/2, we can refer to the common angles in the unit circle and their corresponding cosine values. The cosine function equals -1/2 at the angles 2π/3 and 4π/3 on the unit circle, corresponding to options b) and c) from the question provided.

Step-by-step explanation:

The cosine of an angle equals -1/2 at specific points on the unit circle. To find where cosine equals -1/2, we can refer to the common angles in the unit circle and their corresponding cosine values.

The cosine values for the angles given in the options are: a) π/3 (cosine = 1/2), b) 2π/3 (cosine = -1/2), c) 4π/3 (cosine = -1/2), and d) 5π/3 (cosine = 1/2). Since we are looking for when cosine equals -1/2, the correct answers are b) 2π/3 and c) 4π/3.