18.1 What Is a Circle — Definition and the Secret of Symmetry
Point 4 of 5
18.1.4 The Perpendicular Diameter: One Clean Cut
Core idea
Drop a cut straight down from the center across a chord and it splits both the chord and the arc it spans into two equal halves — a diameter perpendicular to a chord bisects that chord.
Module goal. Start from the one core idea — every point the same distance from a fixed center — to understand the circle, then unearth its most powerful weapon, symmetry, laying the foundation for every theorem to come.
eastmath.com · 18.1 What Is a Circle — Definition and the Secret of Symmetry · 18.1.4 The Perpendicular Diameter: One Clean Cut