Question

For which angle theta is cos theta =-1?
a) 270
b) 360
c) 450
d) 540​

Answer 1

Your answer would be D 540

Answer 2

540°.

Explanation:

On a unit circle, cos θ = -1 at 180°.

However, cos θ has a period of 2π, or 360°. This means that cos θ will equal to -1 again after 2π.

To solve for the angle:

180° + 360° = 540°. This is the next angle at which cos θ = -1.