A circle is a set of points that are equidistant from the center point O. The distance r from the center is called the radius, and. Twice the radius is known as the diameter d = 2 r.
arc: a curved line that is part of the circumference of a circle
chord: a line segment within a circle that touches 2 points on the circle.
circumference: the distance around the circle.
diameter: the longest distance from one end of a circle to the other.
pi (): A number, 3.141592…, equal to (the circumference) / (the diameter) of any circle.
radius: distance from center of circle to any point on it.
sector: is like a slice of pie (a circle wedge).
we did this activity on finding the π, by finding the circumference of an object using a string, and find the diameter using a ruler.