Section 1.4Angles & Their

Measures

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Parts of the Angle

,

, 1

BAC CAB

A or

Possible Names

1

Angle Symbol

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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.

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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

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Angle Addition Postulate

A

B

C

D

m ABD m DBC m ABC

When D is in the interior of angle ABC

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Angle Addition Postulate

A

B

C

Dm ABD

m DBC

m ABC

5x +2

7x +6

72

What is the value of x?

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Congruent Angles

A

B

C D

E

F*

*

If , then

If , then

m ABC m DEF

m ABC m DEF

ABC DEF

ABC DEF

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Angle Names – Acute Angle

9/13

Angle Names – Right Angle

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Angle Names – Obtuse Angle

11/13

Angle Names – Straight Angle

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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