Name: ________________
Geometry CP
Date: _________
Ms. Snyder
Chapter 9: Circles
Notes Section:
9-1 Tangents, Arcs, and Chords
Objective: WWBAT recognize basic vocabulary associated with circles.
Definitions:
Circle: the set of points in a plane at a given distance from a given point in the plane.

o
The given distance is the radius.

Radius: the distance from the center of the circle to the edge of the circle.
o
The given point is the center.
o
All radii (plural of radius) are congruent and named as segments.

Chord: a segment whose endpoints lie on a circle.

Diameter: a chord that contains the center of a circle.

Secant: a line that contains a chord.

Tangent: a line in the plane of a circle that intersects the circle in exactly one point, called the
point of tangency.

Sphere: the set of points in space at a given distance from a given point.

Congruent Circles: circles that have congruent radii.

Concentric Circles: circles that lie in the same plane and have the same center.

A polygon is inscribed in a circle and the circle is circumscribed about the polygon when each
vertex of the polygon lies on the circle.
Examples:
1. What is the relationship between radii and diameters because of their placement in circles?
2. Using the above information, find the missing radii and diameters.
a. Radius = 5 cm, so a diameter = ______.
b. Diameter = 13 in, so all radii = ______.
Point O is the center of the circle. Name each figure on the circle shown below.
3. 𝑂𝑀 =
4. 𝑀𝑁 =
⃡
5. 𝑀𝑁
=
6. 𝑀𝑄 =
7. ⃡𝑀𝐿 =
8. Point M