$\"\"$

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The trigonometric equation is $\"\"$ .

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Rewrite the equation as $\"\"$ .

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

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$\"\"$

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if $\"\"$ , $\"\"$ .

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if $\"\"$ , $\"\"$ .

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if $\"\"$ , $\"\"$ .

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Thus, the solutions are $\"\"$ and $\"\"$ in the interval $\"\"$ . $\"\"$

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