p=4/(2-cosθ )
化为:2p-pcosθ=4
将p=根号(x²+y²),x=pcosθ代入
2根号(x²+y²)-x=4
2根号(x²+y²)=4+x
4(x²+y²)=(4+x)²
3(x²-8/3+16/9)+4y²=16+16...