$\"\"$

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The expression is $\"\"$ .

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Consider $\"\"$ .

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

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$\"\"$ .

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The trigonometric function : $\"\"$ .

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Find the opposite 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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$\"\"$

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$\"\"$ .