Notes

Chapter 4: Systems Based on Numbers

Section 7: Iterated Maps and the Chaos Phenomenon


Exact iterates [in iterated maps]

For any integer a the n^th iterate of x->FractionalPart[a x] can be written as FractionalPart[a^n x], or equivalently 1/2 - ArcTan[Cot[a^n Pi x]]/Pi. In the specific case a=2 the iterates of If[x < 1/2, a x, a (1 - x)] have the form ArcCos[Cos[2^n Pi x]]/Pi. (See pages 903 and 1098.)


From Stephen Wolfram: A New Kind of Science [citation]