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Parametric Equations

x=rcosθ

y=rsinθ

x²+y²=r²

a=2

(x²+y²)²=a²(x²-y²)

r⁴=4(r²cos²θ-r²sin²θ)

r²=4(cos²θ-sin²θ)

r²=4cos2θ

r=±2√(cos2θ)

x=cosθ±2√(cos2θ); y=sinθ±2√cos(2θ)