1. Circles March 18th 2013

2. A ___________ is the set of all point that are a fixed distance, called the _________ from a fixed point, called the _________. A point (x, y) is on the circle if and only if the distance between that point and the center is equal to the radius

3. Distance Formula This is where the equation of a circle originates: So the STANDARD FORM for a circle is: *Do you remember where the distance formula comes from?

4. Example Find an equation of the circle with center (-2, 5) and radius 3.

5. Example Find the equation of a circle with center (2, -6) that passes through the point (0, -6). What is the radius of the circle?

6. Converting to Standard Form If the graph of the equation is a circle, find its center and radius. If the equation has no graph, say so. a.) x 2 + y 2 + 10x – 4y + 21 = 0 b.) x 2 + y 2 – 8x + 6y + 30 = 0 c.) 4x 2 + 4y 2 – 16x – 24y + 36 = 0

7. Example x 2 + y 2 + 10x – 4y + 21 = 0

8. Example x 2 + y 2 – 8x + 6y + 30 = 0

9. Examples 4x 2 + 4y 2 – 16x – 24y + 36 = 0

10. Mathxlforschool.com “Circle”