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The equation is $\"\"$ on the interval $\"\"$ .

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Consider $\"\"$ .

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Double-angle formula: $\"\"$ .

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$\"\"$

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Solve $\"\"$ .

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$\"\"$

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The general solution of $\"\"$ is $\"\"$ ,

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where $\"\"$ is any integer.

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$\"\"$

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For $\"\"$ , $\"\"$ .

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For $\"\"$ , $\"\"$ .

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Therefore, the solutions in the interval $\"\"$ are $\"\"$ .

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$\"\"$ .

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Solve $\"\"$ .

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$\"\"$

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The general solution of $\"\"$ is $\"\"$ ,

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where $\"\"$ is any integer.

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$\"\"$

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For $\"\"$ , $\"\"$ .

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For $\"\"$ , $\"\"$ .

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For $\"\"$ , $\"\"$ .

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For $\"\"$ , $\"\"$ .

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Therefore, the solutions in the interval $\"\"$ are $\"\"$ .

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$\"\"$ .

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The solutions of equation are $\"\"$ .