Solve cos(x)+cos(2x)+cos(3x)=0\cos(x) + \cos(2x) + \cos(3x) = 0cos(x)+cos(2x)+cos(3x)=0 for x∈[0,π]x \in [0, \pi]x∈[0,π].
x=π4,3π4x = \frac{\pi}{4}, \frac{3\pi}{4}x=4π,43π
x=π2,2π3,4π3x = \frac{\pi}{2}, \frac{2\pi}{3}, \frac{4\pi}{3}x=2π,32π,34π
x=π2,2π3x = \frac{\pi}{2}, \frac{2\pi}{3}x=2π,32π
x=π3,2π3,πx = \frac{\pi}{3}, \frac{2\pi}{3}, \pix=3π,32π,π