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X(2), X(3), X(4) 

Q085 is an example of stelloidal quartic i.e. a quartic with four real concurring asymptotes such that two consecutive asymptotes make an angle of 45°. Here these asymptotes concur at G on the curve. This point is called the radial center of the stelloid. This type of curve is also called a harmonic curve since its Laplacian identically vanishes. The polar curves of any degree of any point in the plane are themselves stelloids and when the point lies on the line at infinity their radial centers are G. The figure shows the second polar (a rectangular hyperbola) and the third polar (an equilateral cubic). Their respective asymptotes concur at G. See the related Q125 where several other similar curves are mentioned. 
