1. Find the equation of the circle with radius 3 that is centered at the origin (x, y) 3 x2 + y2 = 32 x2 + y2 = 9 y x

2. Find the equation of the circle with radius r that is centered at the origin (x, y) r x2 + y2 = r2 y x

3. Find the equation of the circle with radius r that is centered at (h, k) (x, y) r (x- h)2 + (y-k)2 = r2 y-k x-h (h, k)

4. Write an equation for the circle with center (5,3) and radius 4 (h, k) (x- h)2 + (y-k)2 = r2 (x - 5)2 + (y - 3)2 = 42 (x - 5)2 + (y - 3)2 = 16

5. Write an equation for a circle if the endpoints of the diameter are at (2, 8) and (2, –2). (2,8) (x- h)2 + (y-k)2 = r2 (2,3) Example 3-2a

6. Write an equation for a circle with center at (3, 5) that is tangent to the y-axis. (h, k) (x - h)2 + (y - k)2 = r2 (x - 3)2 + (y - 5)2 = r2 3 Example 3-3a

7. Find the center and radius of the circle with equation Then graph the circle. (x- h)2 + (y-k)2 = r2 Center: (–3, 0) Radius: 4 Example 3-5a

8. Find the center and radius of the circle with equation Then graph the circle. x2 + 8x + 16 + y2 – 4y + 4 = -11 + 16 + 4 (x + 4)2 + (y – 2)2 = 9 Center: (–4, 2) Radius: 3 (x- h)2 + (y-k)2 = r2 Example 3-5a