# Central Angles and Arcs Notes Jan 29

```GPS Geometry
UNIT QUESTION: What special
properties are found with the parts of
a circle?
Standard: MM2G1, MM2G2
Today’s Question:
How do we use angle measures to
find measures of arcs?
Standard: MM2G3.a,d
Central Angle :
An Angle whose vertex is at the center of the circle
A
Major Arc
Minor Arc
More than 180&deg;
Less than 180&deg;
P
ACB
To name: use
3 letters
AB
C
B
&lt;APB
is a Central Angle
To name: use
2 letters
Semicircle: An Arc that equals 180&deg;
E
D
To name: use
3 letters
EDF
P
F
THINGS TO KNOW AND
REMEMBER ALWAYS
A circle has 360 degrees
A semicircle has 180 degrees
Vertical Angles are Equal
measure of an arc = measure of central angle
A
E
Q
m AB = 96&deg;
m ACB = 264&deg;
m AE = 84&deg;
96
B
C
A
C
B
m ABC = m AB + m BC
Tell me the measure of the following arcs.
m DAB = 240
m BCA = 260
D
C
140
R
40
100
80
B
A
Congruent Arcs have the same measure and
MUST come from the same circle or of
congruent circles.
C
B
45
A
45
D
110
```