Fractional iteration of a function

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The discussion focuses on the concept of fractional iteration of the function f(x) = 6x^5 - 15x^4 + 10x^3, exploring how to transition smoothly from a linear function to its iterated forms. The user seeks guidance on expanding higher-derivative terms in the Taylor expansion to facilitate this process. Despite having a background in calculus and linear algebra, the user feels out of practice and is looking for assistance. The inquiry highlights a gap in understanding the mathematical framework necessary for fractional iteration. Overall, the user is motivated by curiosity rather than academic obligation.
Lord Crc
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I have the following function \begin{align*}<br /> f(x) &amp;= 6x^5 - 15x^4 + 10x^3 &amp; x &amp;\in [0, 1]<br /> \end{align*} and I found that by recursively applying it, that is f(f(x)) etc, I can get new functions with the same s-like shape but steeper slope.

I was curious if there was a way to smoothly go from x (ie a line) to f(x) to f(f(x)) and beyond, and some Googling told me this is called fractional iteration.

However the Wikipedia page didn't leave me with enough clues for finding the appropriate series. In particular I'm struggling to see how to expand the higher-derivative terms in the Taylor expansion in step 4. Any help with this would be appreciated.

FWIW I did go to university and had a fair share of calculus and linear algebra, but it's some 7+ years ago and I'm rusty these days. Oh and this is purely for fun, not homework.
 
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Here is a little puzzle from the book 100 Geometric Games by Pierre Berloquin. The side of a small square is one meter long and the side of a larger square one and a half meters long. One vertex of the large square is at the center of the small square. The side of the large square cuts two sides of the small square into one- third parts and two-thirds parts. What is the area where the squares overlap?

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