$\"\"$

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The equation is $\"\"$ .

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Substitute polar coordinates $\"\"$ and $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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Apply Pythagorean identity: $\"\"$ .

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$\"\"$

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$\"\"$ .

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The polar form equation is $\"\"$ .

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Option C is correct.

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$\"\"$

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Option C is correct.