Circle

A circle is a geometric figure that consists of all points of a plane that are equidistant from a given point of the plane. This point is called the center of the circle . The segment connecting any point of the circle with its center, as well as its length, is called the radius of the circle . AO is the radius.



A segment connecting two points of a circle is called a chord . A chord passing through the center of a circle is called the diameter .



AB - chord, CD - diameter.

A straight line having a single common point with a circle is called a tangent, and their common point is called a tangency point. The radius drawn to the point of tangency is perpendicular to the tangent.



a is the tangent, OA ⊥ a.