1. Intro to Circles
Lesson 1 – 1
Math iii

2. Circle Center Radius Interior Exterior Chord
The set of points in a plane that are a given distance from a point
Center
The point of a circle that all points on the circle are a given distance from
Radius
A segment extending from the center to any point on the circle (plural – radii)
Interior
All points inside the circle
Exterior
All points outside the circle
Chord
A segment joining two points on the circle

3. Chord, secant, tangent, raidus, diameter, circumference, arc, sector, center, common tangent, internal tangent, external tangent, semicircle

4. Diameter Secant Tangent Point of tangency Common Tangent
Any chord containing the center of the circle
Secant
Any line, ray, or segment that contains a chord
Tangent
Any line ray or segment that intersects a circle at only one point
Point of tangency
The point of intersection shared by two tangent figures
Common Tangent
A line, ray or segment that is tangent to 2 circles

6. Ex #1: Use the terms to describe these parts of the figure.
Point O OM
Segment MN
Line MN MQ OR
Segment RV
Line RV

7. In circle O, AO = 5, DB = 2, CDO is a right angle.
Find a, b, and c.

8. Tangent lines form a right angle with a radius drawn to the point of tangency.
If a right angle is not formed, then the line is not truly tangent to the circle.

9. Is AB tangent to the circle at point B?
Is DE tangent to the circle at point E?

10. Tangent Exercises
You are standing 8 ft from a grain silo. The distance from you to a point of tangency on the silo is 16 feet. What is the radius of the silo?
You are standing 10 feet from a pool that is 25’ in diameter. How far are you from the point of tangency to the pool?
You are 15 feet away from a circular water tower. The distance from you to a point of tangency on the tower is 28 feet. What is the diameter of the tower?