$\"\"$

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The equation is $\"\"$ .

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$\"\"$ (Double-angle identity: $\"\"$ )

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$\"\"$ (Simplify)

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$\"\"$ (By factor by grouping)

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$\"\"$

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$\"\"$ (Take out common factor)

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$\"\"$

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$\"\"$ (Apply zero product property)

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$\"\"$

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$\"\"$ . $\"\"$

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The solutions are $\"\"$ .