1. Angles B, ABC or CBA A B C
An angle is formed by two rays that share a common endpoint. A
side
vertex
interior B C
exterior
side
An angle can be named by its vertex or by three letters.
B, ABC or CBA

2. How many angles have their vertex at S?U
An angle cannot be named by its vertex if more than one angle share the same vertex.

3. Numbers can be used to name angles.2 1 3 4 E D
ABE and 1 name the same angle.

4. Angle Measure
The measure of an angle is a measure of rotation.

5. Congruent Angles mX = mY X  Y
If two angles have the same measure, they are congruent. X Y
50º
50º
mY = 50º
mX = 50º
mX = mY
measure of
X  Y

6. A  C Congruent angles can be marked in a diagram with arcs.
In the diagram,
A  C