text: wikipedia gives this\nIn polar coordinates, where the origin is one focus of the ellipse:\n\nr=a(1-e^2)/(1+ecos(theta)) \nby inspection your semimajor axis is 2 = a\nyour semiminor is 3^0.5 so you have an eccentricity of 1/2\n \nhopefully , if I haven't got it completely wrong, \nr=3/2/(1+cos(theta)/2) should be what you want.