This document discusses measuring and classifying angles. It defines an angle as being formed by two rays with a common endpoint called the vertex. Angles are measured in degrees using a protractor and are classified as acute (<90°), right (90°), obtuse (>90° and <180°), or straight (180°). The angle addition postulate states that if a point is within an angle, the measure of the angle equals the sum of the measures of the angles formed by the point and the rays. Congruent angles have the same measure.

1. 1.4 Measure and Classify Angles August 17, 2011
1.4 Measure and Classify Angles
Angle: 2 different rays with same endpoint
Sides
Vertex
Naming Angles
W
WXY or YXW
Y
YXZ or ZXY
X Z
WXZ or ZXW
Measuring Angles
We use protractors to measure an angle
80 90 100
70 110
60 120
100 90 80
50 110 70 130
120 60
40 130 50 140
140 0° 40
30 150
150 30
20 160
160 20
10 170
170 10
0 180 0 180
Classifying Angles
Acute: > 90 37°
133°
Obtuse: <90 and >180
180°
Right: 90 90°
Straight: = 180
HW pg. 28 #4­26 even, 34­42 even 1

2. 1.4 Measure and Classify Angles August 17, 2011
HW pg. 28 #4­26 even, 34­42 even 2

3. 1.4 Measure and Classify Angles August 17, 2011
HW pg. 28 #4­26 even, 34­42 even 3

4. 1.4 Measure and Classify Angles August 17, 2011
Angle Addition Postulate: If P is in the interior of RST, then the
measure of RST is equal to the sum of measures of RSP and PST
m RST = m RSP + m PST
R
m RST
m RSP
S
m PST P
T
HW pg. 28 #4­26 even, 34­42 even 4

5. 1.4 Measure and Classify Angles August 17, 2011
HW pg. 28 #4­26 even, 34­42 even 5

6. 1.4 Measure and Classify Angles August 17, 2011
Congruent Angles: same measure A ≅ B
HW pg. 28 #4­26 even, 34­42 even 6

7. 1.4 Measure and Classify Angles August 17, 2011
HW pg. 28 #4­26 even, 34­42 even 7

8. 1.4 Measure and Classify Angles August 17, 2011
Extra Credit Point if you do this on
the board. Please raise your hand!
HW pg. 28 #4­26 even, 34­42 even 8

9. 1.4 Measure and Classify Angles August 17, 2011
HW pg. 28 #4­26 even, 34­42 even 9

10. 1.4 Measure and Classify Angles August 17, 2011
HW
pg. 28
#4-26 even,
34-42 even
HW pg. 28 #4­26 even, 34­42 even 10