18.6.6 From Shape to Number: How Do You Pin Down a Point on a Circle
Core ideaTo state precisely where a point on a circle sits, you need a whole language for describing numbers — and that is just what the next stage on sets and intervals will answer.
Module goal. Move from the circumference being pi times the diameter to arc length, sector area, and regular polygons, gathering geometry into quantities you can compute, and paving the way for the next stage's use of numbers and intervals to describe shapes.