9.2 Tangents to
Circles
Objectives:
1. Define tangents and secants of circles
2. Understand the geometry of a radius perpendicular to a chord of a circle.
3. Understand the geometry of two tangents that intersect outside of the circle.
1
A line can intersect a circle in two ways.
secant line: tangent line: Tangent means "to touch" in Latin.
Secant means "to cut" in Latin
2
Common Tangents
Common Internal Tangent
Common External Tangent
3
Example 1: Name an example of each
center
C
H
radius
G
B
K
A
F
J
D
E
L
chord
diameter
point of tangency
common external tangent
common internal tangent
secant
4
Tangent Theorems
Theorem 3: Example 2: Is a tangent to circle B?
B
18
6
C
10
A
5
Theorem 4: Example 3: Solve for x.
x2 + 2
11
6