1. What is a radius of a circle? What about the diameter?
Warm-Up
What is a radius of a circle?
What about the diameter?
What is the origin of a graph?
What is the center of a circle?

2. Circle Equations

3. Use equations to graph circles
What we will Learn
Use equations to graph circles
Given points and the radius/diameter give the equation of a circle

4. Circle at the origin

5. What is the equation for a circle with a center at (0, 0) and
Example 1
What is the equation for a circle with a center at (0, 0) and
radius = 5?

6. Circle not on the origin
(x – h)2 + (y – k)2 = r2 when the center is at point (h, k)

7. What is the center and radius of the circle with equation
Example 2
What is the center and radius of the circle with equation
(x+5)+(y-4)=64

8. What are the coordinates of the center of a circle, whose diameter
Example 3
What are the coordinates of the center of a circle, whose diameter
has endpoints at
(–3, 9) and (10, 18)?

9. Example 4

10. Example 5

11. Example