1. Angle Measure
Section 1-4

2. Vocabulary
Degree
Ray
Label
Naming a ray –
AM or AP

3. Opposite Rays
Opposite rays are two rays with a common endpoint that form a line.
R S T
The opposite rays are SR and ST.

4. Angle 2 noncolinear rays that share a common endpoint. Angle Name
R, SRT, TRS, or 1

5. Example 1 Name all of the angles in the diagram below
RTQ, QTS, STR,
1, 2

7. Measuring Angles
The measure of an angle is usually given in degrees. Since there are 360° in a circle, one degree is of a circle. You will use a protractor to find the measures of angles.

8. Example 2 - Find the measure of each angle
Example 2 - Find the measure of each angle. Then classify each as acute, right, or obtuse.
A. WXV
mWXV = 30°
WXV is acute.
B. ZXW
mZXW = |130° - 30°| = 100°
ZXW = is obtuse.

9. Congruent Angles
Congruent angles are angles that have the same measure.

10. An angle bisector is a ray that divides an angle into two congruent angles.
JK bisects LJM; thus LJK  KJM.