$\"\"$

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The trigonometric identity is $\"\"$ .

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Conisder $\"\"$ . \ \

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$\"\"$ \ \

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Apply reciprocal identity: $\"\"$ and $\"\"$ .

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$\"\"$

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Apply pythagorean identity: $\"begin$

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$\"\"$

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$\"\"$

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Apply reciprocal identity: $\"\"$ and $\"\"$ .

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$\"\"$

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$\"\"$ .

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$\"\"$

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$\"\"$ .