1. Do NowDo Now
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2. ObjectiveObjective
 Learn a few more vocabulary terms.Learn a few more vocabulary terms.
 We will find out some rules for circles.We will find out some rules for circles.
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3.  Copy the diagram and the theorem.Copy the diagram and the theorem.
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4. 4 – 28 – 09

5. Inscribed AngleInscribed Angle
 An inscribed angle is an angle with itsAn inscribed angle is an angle with its
vertex on the edge of the circle.vertex on the edge of the circle.
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A
B
C
O

6.  The degree of our central angle is equal toThe degree of our central angle is equal to
the degree of the arc it creates.the degree of the arc it creates.

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S
T
O
50°
»ST =

7. 4 – 28 – 09
S
T
O
67°
SOT∠ = 67°

8. Inscribed Angles!Inscribed Angles!
 TheThe arcarc of an inscribed angle is twice theof an inscribed angle is twice the
degree of the angle.degree of the angle.
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A
B
C
O
30°
60°

9. 4 – 28 – 09
A
B
C
O
70°140°
»AC

10. Ideas to think aboutIdeas to think about
 How many degrees are in a a full circle?How many degrees are in a a full circle?
 How many degrees should a triangles angles sum to?How many degrees should a triangles angles sum to?
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A
B
CO
80°
»
BAC
BOC
ABC
AB
ACB
∠ =
∠ =
∠ =
=
∠ =
110°

11. º
»
90
?
?
?
?
?
60
o
ODC
ODB
CK
BOD
COD
BAC
OBD
∠ =
∠ =
=
∠ =
∠ =
=
∠ =
O
B
C
A
R
D
K