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Question
Solve the following equation:
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Solution
\[\cos4x = \cos2x\]
\[ \Rightarrow 4x = 2n\pi \pm 2x , n \in Z\]
On taking positive sign, we have:
\[4x = 2n\pi + 2x\]
\[ \Rightarrow 2x = 2n\pi\]
\[ \Rightarrow x = n\pi, n \in Z\]
On taking negative sign, we have:
\[ \Rightarrow 6x = 2n\pi\]
\[ \Rightarrow x = \frac{n\pi}{3}, n \in Z\]
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