Section 1.4 Angles & Their Measures 1/13
Dec 13, 2015
Section 1.4Angles & Their
Measures
1/13
Parts of the Angle
,
, 1
BAC CAB
A or
Possible Names
1
Angle Symbol
2/13
Parts of the Angle3/13
Bad Naming Convention
BBad Name!!
A
B
C
DSingle Letter
naming can only be used if it is the vertex for
only ONE ANGLE.
4/13
Geometric Notation
Refers to the NAME of the object (the angle)
Refers to the MEASUREMENT of the object (size of the angle)
ABC
m ABC
A
B
C
5/13
Angle Addition Postulate
A
B
C
D
m ABD m DBC m ABC
When D is in the interior of angle ABC
6/13
Angle Addition Postulate
A
B
C
Dm ABD
m DBC
m ABC
5x +2
7x +6
72
What is the value of x?
7/13
Congruent Angles
A
B
C D
E
F*
*
If , then
If , then
m ABC m DEF
m ABC m DEF
ABC DEF
ABC DEF
8/13
Angle Names – Acute Angle
9/13
Angle Names – Right Angle
10/13
Angle Names – Obtuse Angle
11/13
Angle Names – Straight Angle
12/13
Homework 1.4
P. 29 5 – 8, 26 – 28, 29 – 34 (For #29 – 34, use this diagram)
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B
DE
F
CA