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GEOMETRY Unit 11, Circles
Notes 11-6, Inside and Outside Angles
Name ________________________
Date __________ Period _________
“Inside” and “Outside” Angles
Draw a picture
to illustrate your conjecture
Inside Angle Formula
If an angle is formed by two chords intersecting
inside a circle, then the measure of the angle is
m (Inside Angle) =
Example 1 –
(a)
70°
x°
(b)
116°
160°
(c)
40°
139°
120°
x°
x°
A secant of a circle is a line or line segment that intersects a circle in exactly two
points.
Outside Angle Formula
If an angle is formed by two secants (or tangents)
intersecting outside a circle, then the measure
of the angle is
m(Outside Angle) =
Geometry
8-6, Inside and Outside Angles
Example 2 –
(a)
(b)
(c)
240°
90°
x°
20°
65°
120°
x°
x°
120°
Example 3 –
a) m1 = __________
1
b) m2 = __________
f) m6 = __________
85
80
d) m4 = __________
e) m5 = __________
F
B
c) m3 = __________
A
4
8
6
36
3
O
5
C
7
2
g) m7 = __________
h) m8 = __________
E
D
115