$\"\"$

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The trigonometric function values are $\"\"$ .

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The pythagorean identity is $\"\"$ .

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

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

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

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$\"\"$ (Extract the positive square root) $\"\"$

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The value of $\"\"$ .