Chapter 9
Circle Basics
IN THIS CHAPTER
Defining radii, chords, and arcs
Theorizing about the angle-arc theorems
Practicing products with the power theorems
In a sense, the circle is the simplest of all shapes: no corners, no irregularities, the same simple shape no matter how you turn it. On the other hand, that simple curve involves the number pi 
, and nothing’s simple about that. It goes on forever with no repeating pattern of digits. Despite the fact that mathematicians have been studying the circle and the number 
for over 2,000 years, many unsolved mysteries about them remain. Let’s get started looking at this fascinating shape.
Radii, Chords, and Diameters
Why don’t we begin with the three main types of line segments inside a circle: radii, chords, and diameters:
- Radius: A circle’s radius is the distance from its center to a point on the circle. In addition to being a measure of distance, a radius is also a segment that goes from a circle’s center to a point on the circle. ...
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