Circles Parts of a Circle F F center

Circles

Parts of a Circle F F center Use the center to name a circle.

Parts of a Circle tangent chord diameter radius Segments & Lines secant

Formulas • Radius/diameter radius = ½diameter r=½d diameter = 2(radius) d = 2 r • Circumference C = 2∏r or C = ∏d

Types of Angles Central angle - Vertex is on the center. Inscribed angle - Vertex is on the circle.

Types of Arcs major arc M MNO minor arc P MO semicircle MON O N

Measure of Arcs & Angles minor arc = its central angle major arc = 360 - its central angle 68° 360 – 68 = 292° 68°

Measure of Arcs & Angles minor arc = its central angle major arc = 360 - its central angle semicircle = 180°

Measure of Arcs & Angles minor arc = its central angle major arc = 360 - its central angle semicircle = 180 inscribed angle = ½minor arc 68° 34°

Arc and Chord Relationships A C D If chords are congruent, then arcs are B congruent. then AB CD

Arc and Chord Relationships G If a diameter is A perpendicular to a chord, then H K it bisects the chord. B

Arc and Chord Relationships G If a diameter is A perpendicular to a chord, then H K it bisects the arc. B AH BH

Arc and Chord Relationships Two chords are if and only if O P they are the same distance R B D from the center. A C