$\"\"$

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The value of the trigonometric function $\"\"$ , and the interval is $\"\"$ .

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Double-angle formulas : $\"\"$ ,

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$\"\"$ (or) $\"\"$ ,

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$\"\"$ .

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Find the value of $\"\"$ by using Pythagorean identity.

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Pythagorean identity : $\"\"$ .

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$\"\"$

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The angle $\"\"$ is in the interval $\"\"$ .

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Since cosine function is positive in fourth quadrant, $\"\"$ .

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$\"\"$

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$\"\"$

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The value of $\"\"$ .

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$\"\"$

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$\"\"$

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The value of $\"\"$ .

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$\"\"$

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Quotient identity : $\"\"$ .

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$\"\"$

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$\"\"$

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The value of $\"\"$ .

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$\"\"$

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The values of $\"\"$ , $\"\"$ , and $\"\"$ .