Parts of a Circle
A circle is the set of all points in a plane that are equidistant from a fixed point of the plane called the center of the circle.
All radii of the same circle are congruent.
A circle separates a plane into three sets of points. The position of any point in the plane is determined by comparing the distance from this point to the center with the radius of the circle.
The interior of a circle is the set of all points whose distance from the center of the circle is less than the length of the radius of the circle.
The exterior of a circle is the set of all points whose distance from the center of the circle is greater than the length of the radius of the circle.
There are three kinds of segments related to circles. A radius is a segment whose endpoints are the center of the circle and a point on the circle. A chord is a segment whose endpoints are on the circle. A diameter is the longest chord; it passes through the center of the circle.
Find out more about the parts of a circle by reading the explanation below.
Practice: Identify major arcs, minor arcs, and semicircles and find the measures of arcs and central angles in the following exercises.