Curves85 of 113
Cruciform curve
Terquem, 1847; Pieter Schoute, 1883
Also called the cross curve, or the policeman on point duty curve, this quartic is the image of an ellipse under an inversion in its two axes. Draw a tangent to the ellipse, and through the points where it meets the axes draw parallels to the other axis: they cross on the curve. Its four asymptotes touch the ellipse at its vertices.
x²y² - b²x² - a²y² = 0
On mathcurve.com as Cruciforme