Question

Solve the equation on the interval [0,2π).

8cos^2x+4cosx=0

Select all correct solutions.
0
π/3
π/2
2π/3
π
4π/3
5π/3
3π/2
11π/6

Answer 1

π/2

2π/3

4π/3

3π/2

Explanation:

TTT

Answer 2

π/2, 2π/3, 3π/2, 4π/3.

Explanation:

8cos^2x+4cosx=0

4cosx(2cosx + 1) = 0

so cosx = 0, -1/2.

Therfore

When cos x = 0:

x = π/2, 3π/2

When cos x = -1/2:

x = 2π/3, 4π/3.