$\"\"$

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The trigonometric equation is $\"\"$ .

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Consider $\"\"$ .

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Multiply each side by $\"\"$ .

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$\"\"$

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Inverse property : $\"\"$ .

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$\"\"$

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Using the scientific calculator : $\"\"$ .

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Using the graphing calculator : $\"\"$ .

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Thus, the angle $\"\"$ .

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$\"\"$

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The angle $\"\"$ .