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?