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David

Darling

Devil's curve

Devil's curve

Image: Jan Wassenaar
www.2dcurves.com.


The Devil's curve, also known as the Devil on Two Sticks, is a curve with the Cartesian equation

 

y4 - a2y2 = x4 - b2x2

 

and the polar equation

 

r 2(sin2θ - cos2θ) = a2sin2θ - b2cos2θ.

 

Early studies of it were carried out in 1750 by the Swiss mathematician Gabriel Cramer (1704–1752), who is most famous for his work on determinants, and in 1810 by Lacroix. For a = 25/24, the curve is called the electric motor curve.