Ford Circles and Farey Sequences

Abide By Reason
Feb 7, 2025
5 notes
5 Notes in this Video

Farey Sequences, Mediants, and Adjacent Fractions

FareySequence Mediants RationalEnumeration
01:30

Abide by Reason introduces Farey sequences for viewers who know rational numbers but haven’t seen this structured way to list them with deep number-theoretic properties.

Ford Circles as a Geometric Representation of Rationals

FordCircles RationalGeometry TangencyStructure
05:00

This note targets learners who want a visual picture of the rationals in ([0,1]) beyond points on a line.

Tangency Condition for Ford Circles and Farey Adjacency bc − ad = 1

TangencyCondition FareyAdjacency PythagoreanArgument
09:00

Abide by Reason shows how a simple geometric calculation in the Ford circle picture encodes the same adjacency condition seen in Farey sequences.

Alternating Tangent Circles and Convergence to the Golden Ratio

GoldenRatio FibonacciSequence RationalApproximation
14:30

This note is for learners intrigued by how a simple geometric “walk” among Ford circles recovers the golden ratio.

Farey Walks, Ford Circles, and Diophantine Approximation of Irrationals

DiophantineApproximation FareyWalk RationalApproximants
18:30

Abide by Reason hints at a general method for approximating irrationals using walks through Farey sequences and Ford circles.