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

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Rewrite the equation as $\"\"$ .

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Apply cosine negative angle identity : $\"\"$ .

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$\"\"$

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Apply co-function identity : $\"\"$ .

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$\"\"$

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The general solution of $\"\"$ is $\"\"$ , where $\"\"$ is an integer.

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$\"\"$ .

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$\"\"$

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If $\"\"$ , then $\"\"$ .

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If $\"\"$ , then $\"\"$ .

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If $\"\"$ , then $\"\"$ .

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If $\"\"$ , then $\"\"$ .

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

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The solutions of $\"\"$ in the interval $\"\"$ are $\"\"$ and $\"\"$ .