1. 8.1 The Rectangular Coordinate System and Circles Part 2: Circles

2. Circles An application of the distance formula leads to one of the most familiar shapes in geometry, the circle. A circle is the set of all points in a plane that lie a fixed distance from a fixed point. The fixed point is called the center and the fixed distance is called the radius.

3. Equation of a Circle The equation of a circle of radius r with center at (h, k) is (x – h) 2 + (y – k) 2 = r 2. If the center is at the origin, the equation is x 2 + y 2 = r 2.

4. Finding an Equation of a Circle Find an equation of a circle with center at (-1, 2) and radius 4.

5.  Find an equation of a circle with center at (2, -2) and radius 3.

6. Finding an Equation of a Circle and Graphing Find an equation of the circle with radius 3 and center at (0, 0), and graph the circle.

7.  Find an equation of the circle with center at (4, -3) and radius 5, and graph the circle.

8. Completing the Square and Graphing a Circle Graph x 2 + y 2 + 2x + 6y – 15 = 0.

9.  Graph x 2 + y 2 – 8x – 12y + 3 = 0.