$\"\"$

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The trigonometric function is $\"\"$ .

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$\"\"$ (Write Pythagorean theorem)

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

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$\"\"$ (Apply rule of exponents)

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$\"\"$ (Subtract 16 from each side)

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$\"\"$ (Apply square root each side)

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The trigonometric function, $\"\"$ is positive in quadrant II.

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The trigonometric function $\"\"$ . $\"\"$

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$\"\"$ (Write trigonometric function)

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$\"\"$ (Apply double angle formula: $\"\"$ )

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

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$\"\"$ (Simplify) $\"\"$

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$\"\"$ (Write trigonometric function)

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$\"\"$ (Apply double angle formula: $\"\"$ )

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

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$\"\"$ (Apply rule of exponents)

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$\"\"$ (Apply LCM rule: $\"\"$ )

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$\"\"$ (Simplify) $\"\"$

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$\"\"$ (Write trigonometric function)

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$\"\"$ (Apply formula: $\"\"$ )

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

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$\"\"$ (Simplify) $\"\"$

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The solutions are $\"\"$ .