1. Graphs and Equations of Circles (might want some graph paper) Book: Math 3 (Green Book) Section: 5.2 Circles Quiz: Thursday Circles Test: Sept. 17

2. Standard Equation of a Circle What do you think we need to write an equation of a circle?  Radius  Center  Point on a Circle

3. Let’s See What We Know The point (6, 2) lies on a circle whose center is at the origin. Find the radius.  What formula do we need to use in order to find the radius? DISTANCE FORMULA!!!!!!!

4. Let’s See What We Know The point (-2, -2) lies on a circle whose center is at (4, -5). Find the radius.

5. Let’s Make Some Observations Where is the center? What is the radius? Here is the equation, how is it related to the circle?

6. Let’s Make Some Observations Where is the center? What is the radius? Here is the equation, how is it related to the circle?

7. So we have determined… Let the center of a circle be the point (h,k) and the radius be r The standard equation of a circle is:

8. Write the Equation of the Circle

10. Graph the Circle

12. Write the Equation of the Circle Center: originRadius: 5 Center: (4, -2)Radius:

13. Homework Circles Homework #1 (WS)