Arcs and Chords Recognize and use relationships between arcs and chords. Recognize and use relationships between chords and diameters. Each groove in a round waffle iron is the chord of a circle.
ARCS AND CHORDS The endpoints of a chord are also the endpoints of an arc.
Theorem In a circle or in adjacent circles, two minor arcs are congruent if and only if their corresponding chords are congruent.
A B D E C The chords of adjacent arcs can form a polygon. Quadrilateral ABCD is an inscribed polygon because all of its vertices lie on a circle. Circle E is circumscribed about the polygon because it contains all of the vertices of the polygon. A D B E C
DIAMETERS AND CHORDS Diameters that are perpendicular to chords create special segment and arc relationships.
Theorem In a circle, if a diameter (or radius) is perpendicular to a chord, then it bisects the chord and its arc.
Example 1 Radius Perpendicular to a Chord Circle O has a radius of 13 inches. Radius OB is perpendicular to chord CD, which is 24 inches long. C B X a) If mCD = 134, find mCB D O
Example 1 Radius Perpendicular to a Chord Circle O has a radius of 13 inches. Radius OB is perpendicular to chord CD, which is 24 inches long. C B X a) If mCD = 134°, find mCB D O b) Find OX
Example 2 Chords Equidistant from Center Chords AC and DF are equidistant from the center. If the radius of circle G is 26, find AC and DE. A F B C E G D