1. The problem statement, all variables and given/known data Solve the following trigonomic equation for 0<=x360<= : 5cos2x + cosx + 2 = 0 2. Relevant equations Not sure what goes here but I've been trying to substitute these - cos2x = cos^2x - sin^2x cos2x = 2cosx^2 - 1 - I think this is the correct one to use. cos2x = 1 - sin^2x 3. The attempt at a solution 5cos2x + cosx + 2 = 0 5(2cos^2x-1) + cosx + 2 = 0 10cos^2x + cosx - 3 =0 cosx (10cosx +1) - 3 = 0 ? I get stuck here Am I going about this the right way, or am I completely lost? I think I'm doing it right, I'm just not sure how to continue. Any help appreciated.