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प्रश्न
Solve the following equation:
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उत्तर
\[\cos x + \cos 3x - \cos 2x = 0\]
\[\Rightarrow 2 \cos \left( \frac{4x}{2} \right) \cos \left( \frac{2x}{2} \right) - \cos2x = 0\]
\[ \Rightarrow 2 \cos2x \cos x - \cos2x = 0\]
\[ \Rightarrow \cos2x ( 2 \cos x - 1) = 0\]
\[\Rightarrow \cos2x = 0\] or
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