Circle
The locus (set) of all points in a plane equidistant from a given point called the center of the circle
Concentric circles
Coplanar circles with the same center
Tangent line
A line that intersects a circle in exactly one points called the point of tangency
Tangent segment
A segment of a tangent with one endpoint on a circle
Point of tangency
For a line that intersects a circle in only one point, the point at which they intersect
Arc
A part of a circle that is defined by two endpoints
Minor arc
An arc with a measure less than 180% → named with the 2 endpoints AC or CA
Major arc
An arc with a measure greater than 180% → requires 3 points to name
Semicircle
An arc that measures 180h → named with 3 points begins and ends ends circ of a diameter
Secant
Any line that intersects a circle in exactly two points
AB is a secant
AB is a chord
ABC or BA is a diameter
Central angle
An angle that intersects a circle in two points and has its vertex at the center of the circle → Sides of the angle are radii of the circle
Inscribed angle
An angle that has a vertex on a circle and sides that contain chords of the circle → sides of the angle are chords
Radian measure
The ratio of the arc length to the radius of the circle
Common tangent
A line or segment that is tangent to two circles in the same plane
Common interior tangent
