Just to see how well you guys know about circles! What is the equation for the circumference of a circle?

What is the diameter of a circle (definition)?

What is the radius of a circle (definition)?

What is the equation for a circle?

1. 2r = C

2. The diameter is the length of the line through the center that touches two points on the edge of the circle.

3. Half of the diameter. The length of a line from one point on the edge of a circle to the center.

4.  (x-h)² + (y-k)² = r² where (h,k) is the center and r is the radius.