$\"\"$

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The equation is $\"\"$ .

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Divide each side by negative $\"\"$ .

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$\"\"$

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$\"\"$

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Apply trigonometric inverse property: $\"begin$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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The solution set is $\"\"$ .

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$\"\"$

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The solution set is $\"\"$ .