Find the general solution of the equation cos3θ=−1√2
cos3θ=−1√2
⟹ cos3θ=cos(3π4)
⟹ 3θ=2nπ±3π4n∈Z
∴ \theta = \dfrac{2n \pi}{3} \pm \dfrac{\pi}{4}, \;\;\; n \in Z
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