How Do You Systematically Solve the Equation 2cos²x - cos x = 0?

[Spruance]

Dear all,
How to solve this trigonometric equation systematically?
2cos^(2) x - cos x = 0, where x ∈ [0,360]

Thanks in advance

 

[matt grime]

You can find roots of f(y)=0 when f is any quadratic expression, and given that cos(t)=Z you can find all possible t, so just put those together.