Digits, Grade 7, Volume 1, Homework Helper

## Topic 4: Circles

### 4-1: Center, Radius, and Diameter

#### Key Concept

Parts of a Circle

A circle is the set of all points in a plane that are the same distance from a given point called the center. You name a circle by its center. Circle P is shown.

A diameter is a segment that passes through the center of a circle and has both endpoints on the circle. The term diameter can also mean the length of this segment.

A radius is a segment that has one endpoint at the center and the other endpoint on the circle. The term radius can also mean the length of this segment.

#### Part 1

Intro

You name a segment by its endpoints. Read eh b bar as “segment AB.” The diagram shows eh b bar , comma , b c bar , comma and eh c bar , . .

To refer to the length of a segment, you write the letters without the segment bar. So AB = 3 inches and AC = 3 inches.

Example Naming Diameters and Radii of Circles

An art class developed this logo to represent the school in an art show. Determine which segments are radii and which are diameters.

table with 2 rows and 4 columns , row1 column 1 , p c bar , column 2 eh d bar , column 3 eh p bar , column 4 eh b bar , row2 column 1 , eh c bar , column 2 p d bar , column 3 p b bar , end table

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