$\"\"$

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The trigonometric equation is $\"\"$ .

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Consider $\"\"$ .

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Apply formula : $\"\"$ .

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$\"\"$

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$\"\"$

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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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Divide each side by 3.

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$\"\"$ .

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General solution is $\"\"$ , where $\"\"$ is an integer.

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Find the angle in the interval $\"\"$ .

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General solution is $\"\"$ , where $\"\"$ is an integer.

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

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

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

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

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

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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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$\"\"$

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