botanic curve

roulette

last updated: 2004-12-04



The botanic curve is the conchoid of the rhodonea.
Its name is derived from her petal-like form.

Other names for the curve are:

The following qualities of the rhodonea hold also for the botanic curve:

  • the number of petals is the denominator of 1/2 - 1/(2c)
  • for integer values for c the number of petals is c (c odd), or 2c (c even)
  • when c is irrational the curve does not close, and the number of petals is infinite
  • when the parameter c is rational, the resulting curve is algebraic

The following botanic curves have been given a special name:

c curve
1/2 Freeth's nephroid
1 limašon of Pascal
2 Ceva's trisectrix

Some examples for other values of c:



You can observe that the value of d defines the form of the petals: for d < 1 the petal is open, it closes for d=1 and it forms an extra small petal for d>1.

John Baines made a Flash script to produce the curve.