Download Section 1.4

Chapter 1
Section 1.6
How do you measure, name and classify
angles? What is the Angle Addition
Postulate?
How do you identify angle pairs?
Warm up
 In your books, page 36, 1-6 at very top
Angles
 A figure formed by two rays that have the same endpoint.
 The two rays are called the sides of the angle
 The common endpoint is called the vertex.
 Can be named as B,ABC or1
 I prefer ABC or  1
 Make sure that the vertex is the
middle point.
A

B
1

C
Angle Classification
 Acute Angle – an angle measuring between 0 and 90 degrees
 Right Angle – an angle measuring 90 degrees
 Obtuse Angle – an angle measuring between 90 to 180
degrees
 Straight Angle – an angle measuring 180 degrees
Classify these angles
Congruent Angles
Angles with the same measure
Challenge!
 You and your partner figure out how many angles there are
Postulate 1-8: Angle Addition Postulate
 If point B lies in the interior ofAOC, then
m AOB + m BOC =mAOC
C
B
O
A
If AOC is a straight angle and B is any point not on line AC,
then
m AOB + mBOC =180
B
A
O
C
Example
 The measure of angle AOB is x and the measure of angle
BOC is x+3. The measure of angle AOC is 55 degrees.
What is angle AOB and angle BOC?
C
B
O
A
Special Angle Pairs
Vertical Angles
Complimentary Angles – two
angles whose measures add
up to 90
Adjacent Angles – common
side, common vertex, no
common interior points
Supplementary Angles – two
angles whose measures add
up to 180
Adjacent Angles
ADJACENT
NOT ADJACENT
4
1
3
4
3
2
1
4
2
3
Example - Identifying Angle Pairs
In the diagram below, identify all types of the following:
Complementary
Supplementary
Vertical
Homework
 Page 40-41 1-8, 13-40, 42-45