14 terms

# Circles

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a segment whose endpoints are at the center of the circle and on the circle
Chord
a segment whose endpoints are points on the circle
Diameter
a chord that passes through the center of the circle (the longest chord in a circle)
Secant
a line that intersects the circle in exactly two points
Tangent
a line that intersects the circle at exactly one point
Concentric Circles
circles on the same plane that have a common center
Central Angle
an angle with its vertex at the center of the circle
Arc
an unbroken part of a circle, any two points on a circle are the endpoints of the arc between them
Minor Arc
an arc measuring less than 180º; minor arcs are named using the arc's endpoints with an arched hat; the measure of a minor arc is equal to the endpoints of its central angle
Major Arc
an arc measuring more than 180º, but less than 360º; major arcs are named for the endpoints and a point between them; the measure of a major arc is equal to 360º minus the measure of its minor arc
Semicircle
an arc whose endpoints are on a diameter of the circle; a semicircle also uses three letter notation; a semicircle measures 180º