$\"\"$

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The rectangular equation is $\"\"$ .

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

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

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$\"\"$ $\"\"$

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$\"\"$ (Take out common factor)

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$\"\"$ (Divide each side by $\"\"$ )

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$\"\"$

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$\"\"$ (Double - angle formula : $\"\"$ )

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

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The polar form is $\"\"$ .