Find all solutions on interval [0, 2pi] for cos(x)+sin(2x)=0

[KingAce]

Find all solutions on interval [0, 2pi] for cos(x)+sin(2x)=0

I need a refresher; I have an exam coming up, and I've forgotten how to do these type of problems. Please help! Thanks!

 

[pka]

\(\displaystyle \begin{array}{l} \cos (x) + \sin (2x) = 0 \\ \cos (x) + 2\sin (x)\cos (x) = 0 \\ \cos (x)\left( {1 + 2\sin (x)} \right) = 0 \\ \end{array}\)