$\"\"$

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The trigonometric function is $\"\"$ .

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Now we can find $\"\"$ .

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Apply Pythagorean identity: $\"\"$ .

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$\"\"$ (Substitute $\"\"$ )

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$\"\"$ $\"\"$

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$\"\"$ (Subtract $\"\"$ from each side) \ \

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ (Take square root of each side) \ \

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$\"\"$

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$\"\"$

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$\"\"$

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The value of $\"\"$ .