Wed. 10/30/13 G.G.71 Write equation of a circle, given its center and radius UR Group: Obniel, Raudo, Perla, & Dewel

Raudo [posed the question]: How do we know which point to use in writing the equation of a circle if they give us all these points?

Obniel: Let’s read further Perla: Oh, we need the midpoint formula Dewel: No, I think we need the distance formula Perla: Wait we need to find equation of a circle Raudo: Oh, we need the center and the radius

Obniel: Why? Raudo: Because equation of a circle is: (x - h) 2 + (y – k) 2 = r 2 (h, k) is the center and r is the radius

Raudo: The center is (0,0) and radius is 5

(x - h) 2 + (y - k) 2 = r 2 (x - 0) 2 + (y - 0) 2 =(5) 2 (x – 0) 2 + (y – 0) 2 = 25 or Obniel [wrote]: X 2 + Y 2 = 25 Raudo: The center is (0,0) and radius is 5

Take away: Perla make connection that midpoint of a diameter is a synonym for center General equation of a circle is: (x – h) 2 + (y – k) 2 = r 2 Where (h, k) is center and r is radius Raudo and Obniel said we can write: (x – 0) 2 + (y – 0) 2 = 25 OR X 2 + Y 2 = 25