GEOMETRY Chapter:Circle Terminology What is Circle? • A circle is a two-dimensional figure formed by a set of points that are at a fixed distance (radius) from a fixed point (center) on the plane. The fixed point is called the origin or center of the circle and the fixed distance of the points from the origin is called the radius. Observe the following figures to see the basic parts of a circle, the center, the radius, and the diameter of a circle. 1) Radius A • The segment joining the center of a circle to a point on the circle. O • Example: OA is the radius and O is the center of the cercle 2) Chord • A segment joining two points on a circle B • Example 01: AB A C B • Example 02: AB C A 3) Diameter • A chord that passes through the center of a circle. A O • Example: AB B 4) Secant A • A line that intersects the circle at exactly two points. C O • Example 01: AB D B A C • Example 02: AB O D B 5)Tangent B C • A line that intersects a circle at exactly one point. A • Example: AB 6) Central Angle A • An angle whose vertex is at the center of a circle. B • Example: Angle ABC C 7)Inscribed Angle B A C • An angle whose vertex is on a circle and whose sides are determined by two chords. • Example: Angle ABC 8) Arc • A figure consisting of two points on a circle and all the points on the circle needed to connect them by a single path. • Example: arc AB B A