Circles

A circle is the set

A circle is the set of all points in a plane equidistant from a fixed point called the center. Key terms include: Radius (r) - distance from center to

Circumference C = 2πr = πd

Circumference C = 2πr = πd, where π ≈ 22/7 ≈ 3.1416. The ratio C/d = π is constant for all circles. This fundamental constant was first calculated by

THEOREM

THEOREM: The perpendicular from the center of a circle to a chord bisects the chord. CONVERSE: The line joining the center to the midpoint of a chord

THEOREM 1

THEOREM 1: Equal chords subtend equal angles at the center. THEOREM 2: Equal chords are equidistant from the center. THEOREM 3: Chords equidistant fro

The degree measure of an arc

The degree measure of an arc equals the angle it subtends at the center. Minor arc < 180°, Major arc > 180°, Semicircle = 180°. THEOREM: Two arcs are