$\"\"$

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The trigonometric equation is $\"\"$ .

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$\"\"$ (Apply double angle identity: $\"\"$ ) \ \

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$\"\"$ (Add $\"\"$ ) \ \

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$\"\"$

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$\"\"$

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

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

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$\"\"$ $\"\"$

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$\"\"$ $\"\"$

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$\"\"$ $\"\"$ \ \ $\"\"$

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The solutions are $\"\"$ .