1. Circles: Basic Terms Tutorial 8a

2. Parts of a Circle  A circle is the set of all points in a plane equidistant from a given point.  Name a circle by its center: P The center of the circle below is point P. Circle P. Therefore the name of this circle is Circle P.

3. Parts of a Circle  A radius is a segment that has one endpoint at the center and the other endpoint on the circle. Radius plural is radii. P Circle P C A B The following segments are radii of Circle p. PC, PB, PA

4. Parts of a Circle  A chord is a segment whose endpoints lie on the circle. P Circle P C A  A diameter is a chord that contains the center of the circle.  A diameter is twice as long as the radius. is a diameter of Circle P. BC B BC = 2(BP) D is a chord of Circle P. AD

5. Parts of a Circle  A secant is a line that contains a chord of a circle. P Circle P A  A tangent is a line in the same plane as a circle that intersects the circle in exactly one point.  The point of tangency is the point of intersection. is tangent to Circle P. GE D is a secant of Circle P. AD F E G