$\"\"$

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The expression is $\"\"$ .

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Let $\"\"$ , then $\"\"$ .

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The trigonometric function : $\"\"$ .

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Find the adjacent side by using pythagorean theorem :

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$\"\"$ .

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$\"\"$

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$\"\"$ .

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$\"\"$

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Thus, $\"\"$ .

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$\"\"$

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$\"\"$ .