How does the equation of a circle relate to its center and radius?
Begin with the radius: drag the black dot around to change the radius of the circle. [*]As you change the radius, what part of the equation changes? [*]How does that part change? [*]What can you conclude about the equation of a circle and its radius? Now go to the center: drag the red dot around to change the center of the circle. You can also drag the circle itself. [*]As you change the center, what part of the equation changes? [*]How does that part change? [*]What can you conclude about the equation of a circle and its center?