1. Center, Radius, and Diameter

2. What are the relationships among the parts of a circle?
Focus Question
What are the relationships among the parts of a circle?

3. Key Concept
A CIRCLE is the set of all points in a plane that are the same distance from the given point called the CENTER.

4. Key Concept
You name a circle by its center.
Circle P is shown.

5. A DIAMETER is a line segment that passes through the center of a circle and has both endpoints on the circle.

6. Parts of a Circle
A RADIUS is a segment that has one endpoint at the center and the other endpoint on the circle.

7. Examples—Part 1
You name a segment by its endpoints. Read AB as “segment AB.”
The diagram shows AB , AC , and BC .

8. Examples—Part 1
To refer to the length of a segment, you write the letters without the segment bar.
So AB=3 in. and BC=3 in.

9. Examples—Part 1
An art class developed this logo to represent the school in an art show.
Determine which segments are radii.

10. Examples—Part 1
An art class developed this logo to represent the school in an art show.
Determine which segments are diameters.

11. Examples—Part 1
How many radii are shown?

12. Examples—Part 2

13. Examples—Part 2
The distance from a car to the center of the Ferris wheel is ft.
Approximately how tall is the Ferris wheel?

14. Examples—Part 2
In the diagram, ST=4 1/3 ft
What is SO?

15. Examples—Part 3 3x - 1 = 5 3x = 6 x = 2
The expression 3x−1 represents the diameter of the orange slice.
What is the value of x ?
3x - 1 = 5
3x = 6
x = 2

16. Examples—Part 3 2x - 4 = 24 2x = 28 x = 14
If KM=2x−4 and LM=12, what is the value of x ?
2x - 4 = 24
2x = 28
x = 14

17. Review: HW: What is a radius? What is a diameter?
How does the radius relate to the diameter?
Review:
HW:
Radius and Diameter worksheet