Curves109 of 113
Devil’s curve
Gabriel Cramer, 1750
The quartic y⁴ - b²y² = x⁴ - a²x². Its middle is an hour-glass, upright while b is less than a and lying down once b is greater, with a circle between, and four arms run off to infinity around it. The name is said to come from the diabolo, whose spinning top the hour-glass resembles.
y⁴ - b²y² = x⁴ - a²x²
On mathcurve.com as Courbe du diable