1.
Arc: consists of two points on a circle and all the points on the circle that is needed to connect them
2.
Arc to Central Angle Theorem: If two arcs of a circle (or of congruent circles) are congruent than the corresponding central angles are congruent
3.
Arc to Chord Theorem: If two arcs of a circle (or of congruent circles) are congruent, then the corresponding chords are congruent
4.
Center: the middle of the circle that is a given distance from the edge of the circle
5.
Central Angle: an angle whose vertex is at the center of the circle
6.
Central Angle to Arc Theorem: If two central angles of a circle (or of congruent circles) are congruent, then their intercepted arcs are congruent
7.
Central Angle to Chord Theorem: If two central angles of a circle (or of congruent circles) are congruent, then the corresponding chords are congruent
8.
Chord: a segment that joins any two points on a circle
9.
Chord Bisector Theorem: If a radius of a circle bisects a chord that is not a diameter, then it is perpendicular to that chord
10.
Chord to Arc Theorem: If two chords of a circle (or of congruent circles) are congruent, then the corresponding arcs are congruent
11.
Chord to Central Angle Theorem: If two chords of a circle (or of congruent circles) are congruent, then the corresponding central angles are congruent
12.
Chord-Chord Angle: An angle formed by two chords that intersect inside a circle, but not at the center
13.
Chord-Chord Power Theorem: If two chords of a circle intersect inside the circle then the product of the measures of the segments of one chord is equal to the product of the measures of the segments of the other chord
14.
Circle: a set of all points in a plane that are a given distance from a given point in the plane.
15.
Circumcenter: The center of a circle circumscribed about a polygon
16.
Circumference: The perimeter of a circle (pie x diameter)
17.
Circumscribed Polygon: A polygon in which each of its sides is tangent to the circle
18.
Common External Tangent: A common tangent that is not between the circles (it does not intersect the segment that joins the centers)
19.
Common Internal Tangent: A common tangent that lies between the circles (it also intersects the segment joining the centers)
20.
Common Tangent: A line that is tangent to two circles (not necessarily at the same point)
21.
Concentric: two or more coplanar circles with the same center
22.
Congruent Chord Theorem: If two chords of a circle are congruent, then they are equidistant from the center of the circle
23.
Congruent Circles: two circles are congruent if they have congruent radii
24.
Diameter: a chord that passes through the center of the circle
25.
Equidistant Chord Theorem: If two chords are equidistant from the center, then they are congruent
26.
Exterior Point: a points thats outside the circle
27.
External Part: The part of a secant segment that joins the outside point to the closer intersection point
28.
Externally Tangent Circles: Tangent circles where the two circles are next to each other and the tangent is between them
29.
Incenter: The center of a circle inscribed in a polygon
30.
Inscribed Angle: An angle whose vertex in on the circle and has sides that are chords
31.
Inscribed Parallelogram Theorem: If a parallelogram is inscribed in a circle, it must be a rectangle
32.
Inscribed Polygon: A polygon in which all of its vertices lie on the circle
33.
Inscribed Quadrilateral Theorem: If a quadrilateral is inscribed in a circle, its opposite angle are supplementary
34.
Intercepting Arc Theorem: If two inscribed or tangent-chord angle intercept the same arc or congruent arcs then the angles are congruent
35.
Interior Point: a point thats inside the circle
36.
Internally Tangent Circles: Tangent circles where one circle lies inside the other
37.
Length of an Arc Theorem: The length of an arc is equal to the circumference of its circle times the fractional part of the circle determined by the arc
Arc Length = (arc measure/360) x circumference
38.
Major Arc: an arc whose measure is greater than 180 degrees
39.
Measure of a Major Arc: the measure of this arc is equal to 360 minus the measure of the minor arc with the same endpoints.
40.
Measure of a Minor Arc: the measure of this arc is equal to the central angle that intercepts the arc
41.
Minor Arc: an arc whose measure is less than 180 degrees
42.
Perpendicular Chord Bisector Theorem: The perpendicular bisector of a chord passes through the center of the circle
43.
Perpendicular Chord Theorem: If a radius is perpendicular to a chord, then it bisects the chord
44.
Point of Tangency: The point where a tangent line intersects a circle
45.
Radius: the given distance from the center to the points on the circle
46.
Secant: A line that intersects a circle at exactly two points
47.
Secant Segment: The part of a secant line that joins a point outside the circle to the intersection point on the other side of the circle.
48.
Secant-Secant Angle: An angle whose vertex is outside a circle and that has sides that are both secants
49.
Secant-Secant Power Theorem: If two secant segments are drawn from an external point to a circle, then the product of the measures of one secant segment and its external part is equal to the product of the measures of the other secant segment and its external part
50.
Secant-Tangent Angle: An angle whose vertex is outside a circle and that has one side that is a secant and one side that is a tangent
51.
Semicircle: an arc whose endpoints are the endpoints of the diameter
52.
Semicircle Theorem: An angle inscribed in a semicircle is a right angle
53.
Tangent: A line that intersects a circle at exactly one point
54.
Tangent Circles: Circles that intersect at exactly one point
55.
Tangent Postulate: A tangent line is perpendicular to the radius that is drawn to the point of tangency
56.
Tangent Segment: The part of a tangent line that is between the point of tangency and a point outside the circle
57.
Tangent-Chord Angle: An angle whose vertex is on the circle and has one side that is a tangent and one side that is a chord
58.
Tangent-Secant Power Theorem: If a tangent segment and a secant segment are drawn from an external point to the circle, then the square of the measure of the tangent segment is equal to the product of the measures of the entire secant segment and its external part
59.
Tangent-Tangent Angle: An angle whose vertex is outside a circle and that has sides that are both tangents.
60.
Tangent-Tangent Measure Theorem: The sum of the measures of a tangent-tangent angle and its minor arc is 180
61.
Two-Tangent Theorem: If two tangent segments are drawn to a circle from an external point, the those segments are congruent
62.
Vertex Inside the Circle Measure Theorem: The measure of a chord-chord angle is one-half the sum of the measures of the arcs intercepted by the chord-chord angle and its vertical angle
63.
Vertex on Circle Measure Theorem: The measure of an inscribed angle or tangent-chord angle (vertex on a circle) is one-half the measure of its intercepted arc
64.
Vertex Outside the Circle Measure Theorem: The measure of a secant-secant angle, a secant-tangent angle, tangent-tangent angle (vertex outside a circle) is one-half the difference of the measures of the intercepted arcs
