$\"\"$

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The expression is $\"\"$ .

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consider $\"\"$

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$\"\"$ .

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The expression becomes $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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From trigonometric identities $\"\"$ .

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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 exact value of expression $\"\"$ .

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$\"\"$

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The exact value of expression $\"\"$ .