1. The problem statement, all variables and given/known data Solve 2cos(x)^2 + 3cos(x) + 1 = 0 for 0 <= x <= 2pi 2. Relevant equations Trigonometric equations, yadda yadda yadda. 3. The attempt at a solution 2cos(x)^2 + 3cos(x) + 1 = 0 cos(x)(2cos(x) + 3) = -1 cos(x) = -1/(2cos(x) + 3) I then figured out that you get a solution when cos(x) = -1 (so x = pi). However, there are supposed to be multiple solutions, and I don't know how to find these. Any pointers?