1. 9.3 - Circles Objectives: Write an equation for a circle given sufficient information. Given an equation of a circle, graph it and label the radius and the center. Standard: 2.8.11.E. Use equations to represent curves.

2. A locus problem involves an equation that represents a set of points that satisfy certain conditions. A circle is the set of all points in a plane that are a constant distance, called the radius, from a fixed point, called the center.

3. Example 1a

4. Example 1b**  Write the standard equation of the circle whose center is at the origin and whose radius is 2. Sketch the graph.

6. Example 2

7. Example 3

8. Example 4** Tell whether A(2, 1) is inside, outside, or on the circle whose center is at (-2, 3) and whose radius is 4.

9. Writing the equation of a translated circle – completing the square Example 5a

10. Example 5b** Write the standard equation for the circle. State the coordinates of its center and give its radius. Then sketch the graph.

12. Homework Pg. 583-584 #8-74 even