1. Circles in the Coordinate Plane
Lesson #124

2. Circle: The locus of points equidistant from one point.
Find all of the points r distance away from the point (h, k).
(h, k)

3. Standard Form: (x – h)2 + (y – k)2 = r2
Center of the circle =
Radius of the circle =
Examples:
1. Write the equation of the circle with a center at (3, -2) and a radius of length 7.

4. 2. Given the circle: (x – 1)2 + (y – 5)2 = 36
a. What are the coordinates of the center of the circle?
What is the length
of the radius?
Graph the circle.
d. Give two points that
are on the circle.

5. 3. Given the circle: x2 + y2 = 50
a. What are the coordinates of the center of the circle?
b. What is the length of the radius?

6. 4. Given the circle: (x + 2)2 + y2 = 9
a. What are the coordinates of the center of the circle?
What is the length
of the radius?
Graph the circle.
d. Give two points that
are on the circle.

7. Find the center and radius of the circle whose equation is (x – 3)2 + (y – ½)2 = 18.
6. Write the equation of the circle with a center at (-3,4) and a radius of

8. How can you graph this in the calculator?
(x – 1)2 + (y – 5)2 = 36