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(a)

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

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Find $\"\"$ .

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Double-angle formula : $\"\"$ .

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Reciprocal identity: $\"\"$ .

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If $\"\"$ , then $\"\"$ .

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Find the value of $\"\"$ .

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Pythagorean identity: $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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(b)

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Find $\"\"$ .

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Double-angle formula: $\"\"$ .

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Substitute $\"\"$ .

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$\"\"$

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(c) Find $\"\"$ .

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Half-angle formula: $\"\"$ .

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Substitute $\"\"$ .

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$\"\"$

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Since $\"\"$ and $\"\"$ , $\"\"$ lies in the fourth quadrant.

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$\"\"$ , then $\"\"$ lies in the second quadrant.

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Therefore, $\"\"$ is positive.

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$\"\"$ .

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(d)

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Find $\"\"$ .

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Half-angle formula: $\"\"$ .

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Substitute $\"\"$ .

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$\"\"$

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Here $\"\"$ , $\"\"$ is negative.

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$\"\"$ .

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(a) The exact value of $\"\"$ .

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(b) The exact value of $\"\"$ .

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(c) The exact value of $\"\"$ .

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(d) The exact value of $\"\"$ .