VOCABULARY
Circle
Center
Set of all points
A point that is
_________________
________________ from
from all points on the
a given point
circle.
Radius
Chord
Segment from the
A segment with
__________ to any point
____________ on the
on the circle
circle
Diameter
Secant
A chord that contains the
________ of the circle
A line that intersects a
circle in
_______________
Tangent
A line in the plane of the circle that
intersects the circle in
_____________ 1 point
Example 1
Tell whether the line, ray, or segment is best described as a radius, chord,
diameter, secant, or tangent of ОC.
a.
BC
d.
b.
AF
e.
c.
AF
AB
ED
1
Example 2
Using the circle to the right, identify the name of each:
C
Circle Name ___________
D
B
Radius __________
A
Diameter _________
Chord ___________
E
G
Tangent _________
F
Secant __________
THEOREM 10.1
In a plane, a line is _______________ to a circle if and only if
the line is _______________________ to a radius of the circle
at its endpoint on the circle.
Example 3: In the diagrams below, is ST tangent to Circle R?
Example 4: In the diagram, B is a point of tangency. Find the radius r of ОC.
2
THEOREM 10.2
Tangent segments from a common external point are
________________
Example 5
RS is tangent to C at S and RT is tangent to C at T Find the value(s) of x.
2x + 3
S
R
C
3x - 4
T
Example 6
RS is tangent to C at S and RT is tangent to C at T Find the value(s) of x.
3