$\"\"$

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The expression is $\"\"$ , $\"\"$ is in second quadrant.

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(a) Find $\"\"$ .

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Apply trigonometric identity: $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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Since $\"\"$ is in second quadrant, $\"\"$ .

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$\"\"$

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$\"\"$ .

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$\"\"$

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(b) Find $\"\"$ .

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Apply sum formula: $\"\"$ .

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$\"\"$

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Substitute $\"\"$ and $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$

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(c) Find $\"\"$ .

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Apply difference formula: $\"\"$ .

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$\"\"$

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Substitute $\"\"$ and $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$

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(d) Find $\"\"$ .

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Apply sum formula: $\"\"$ .

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$\"\"$

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Substitute $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$ .

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$\"\"$

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(a) $\"\"$ .

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(b) $\"\"$ .

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(c) $\"\"$ .

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(d) $\"\"$ .