$\"\"$

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The equation is $\"\"$ .

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Consider $\"\"$ .

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Multiply each side by $\"\"$ .

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$\"\"$

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Apply double angle formula : $\"\"$ .

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$\"\"$

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$\"\"$

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Substitute $\"\"$ in above equation. \ \

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$\"\"$ .

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Thus, the rectangular equation is $\"\"$ . $\"\"$

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The rectangular equation is $\"\"$ .