
Circle: set of all points equidistant from a given point. A
circle is 360°.

Center of a Circle: the central point from which all the
points are equidistant; a circle is named by its center

Radius: segment that has one endpoint at the center and
the other endpoint on the circle

Congruent Circles: circles with congruent radii

Diameter: a segment that contains the center of the
circle and has both endpoints on the circle

Central Angle: an angle whose vertex is the center of the
circle

Semicircle: a type of arc that is half a circle
Minor Arc: smaller than a semicircle
Major Arc: bigger than a semicircle
Adjacent Arcs: arcs of the same circle that have exactly one
point in common.
Circumference: the distance around the circle
Concentric Circles: circles that lie in the same plane and
have the same center
Arc Length: a fraction of a circles circumference
Congruent Arcs: arcs that have the same measure and are in
the same circle or in congruent circles.
Name each of the following:
1. Circle
C
2. Center
3. Radius
F
4. Diameter
5. Central angle
6. Semicircle
E
7. Minor arc
A
8. Major arc
9. Adjacent arcs
Concentric
Circles
D
B
Arc Addition Postulate (Post. 7-1):
The measure of the arc formed by
two adjacent arcs is the sum of the
measures of the two arcs.
The measure of an arc is the
degree of its central angle!
Circumference of a Circle (Thm. 7-13):
The circumference of a circle is pi
times the diameter.
Arc Length (Thm. 7-14): The length of
an arc of a circle is the product of the
ratio, measure of the arc : 360, and the
circumference of the circle.