radius chord diameter secant tangent center

--the set of points in a plane equidistant from a given point known as the center.

C Point C is the center P 5 is the radius of Circle C. 5 is a radius

A circle divides a plane into three sets of points: interior points, exterior points, points on the circle.

C r P If CP < r, then P is an interior point.

C r P If CP >r, then P is an exterior point.

C r P If CP = r, then P is on the circle. r

C P r Radius : a segment with one endpoint at the center of the circle and the other endpoint is a point on the circle. All other points are INTERIOR points

C Chord : a segment with both endpoints ON the circle. ALL OTHER POINTS ARE INTERIOR POINTS

Diameter: a chord that contains the center of the circle

SECANTS

A line, a segment a ray

Secant: a line, a segment, or a ray that intersects the circle in two distinct points and contains interior and exterior points.

Tangent: a line, a segment, or a ray, coplanar with the circle, intersects the circle in exactly one point (called the point of tangency), and all other points are exterior points.

A segment or ray is tangent to a circle only if the LINE that contains the segment or ray is tangent to the circle.

A B EXAMPLE: AB is not tangent to the circle since AB is not tangent to the circle.

ARC: The portion of a circle between and including two of its points. O A B X

ARC: An arc is measured in degrees ( ). O A B X

ARC CLASSIFICATIONS: MINOR ARC: has a measure less than 180 O A B X A minor arc is named by its two endpoints.

ARC CLASSIFICATIONS: MAJOR ARC: has a measure greater than 180 O A B X A major arc is named by its two endpoints and a direction point.

ARC CLASSIFICATIONS: SEMICIRCLE: has a measure equal to 180 A semicircle is named by its two endpoints and a direction point. O A B C X

ARC CLASSIFICATIONS: SEMICIRCLE: has a measure equal to 180 A semicircle is determined by the endpoints of a diameter. O A B C X