CurvG
Classic Cartesian curves

Serpentine curve

y = abx/(x² + a²): an S-bend that rises to b/2, falls back and fades to the x-axis on both sides.

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Formulas and key values

Cartesian equation
y=abxx2+a2y = \frac{abx}{x^2 + a^2}
Maximum
(a, b2)\left(a,\ \frac{b}{2}\right)
Inflection points
x=0, ±3 ax = 0,\ \pm\sqrt3\,a
Asymptote
y=0y = 0

a is where the bend peaks and b twice its height.

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01 · Definition

What is the Serpentine curve?

The serpentine is a cubic curve that winds like a snake through the origin. It was studied by l’Hôpital and Huygens in the 1690s, and Isaac Newton gave it its name in his enumeration of cubic curves.

Written as a function, y = abx/(x² + a²), it is easy to analyse: an odd function with a maximum b/2 at x = a, a minimum −b/2 at x = −a, inflection points at x = 0 and x = ±√3·a, and the x-axis as its asymptote in both directions.

02 · Properties

Key properties

  1. Maximum b/2 at x = a; minimum −b/2 at x = −a.
  2. Inflection points at x = 0 and x = ±√3·a.
  3. The x-axis is an asymptote on both sides.
  4. Odd function: symmetric about the origin.
  5. Named by Newton in his classification of cubic curves.

03 · Questions

Serpentine curve: common questions

What is the equation of the Serpentine curve?
Cartesian equation: y = abx/(x^2 + a^2). a is where the bend peaks and b twice its height.

04 · Keep exploring