$\"\"$

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The trigonometric expression is $\"\"$ .

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Consider $\"\"$ then $\"\"$ .

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The equation is $\"\"$ .

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Double angle formula : $\"\"$ .

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Substitute $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$

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The solution for $\"\"$ is $\"\"$ .