Determine the sum of all x∈[0,2π]x \in [0, 2\pi]x∈[0,2π] such that cos(2x)+cos(x)=0\cos(2x) + \cos(x) = 0cos(2x)+cos(x)=0.
2π2\pi2π
3π3\pi3π
4π4\pi4π
5π5\pi5π