Solving an equation in a specified interval

__The Question: __Solve the equation in the interval 0 __<__ *θ *__<__ 2 pi.

cos *θ *+ cos2 *θ + *sin2* =* 0

__Attempted Solution:__ Well, my hunch was to factor this equation. But, at least to my innumerate eye, it looks as if it cannot be factored. I am a bit confused by the structure of this equation. I'm not use to seeing anything like "sin" without a *θ*. The answers probably really easy and maybe it's just tiredness preventing me from seeing the solution, but could someone help?