Chapter 1Section 1.4

Angles and Their Measures

Angle: Composed of two rays that have the same initial point

Sides

Vertex

A

B•

•C

AisvertexThe

ACandABsideshasangleThe The angle can be named by

BAC, CAB, or A

Interior

Exterior

Name the 3 angles in the picture

1. PQS Top angle

2. SQR Bottom angle

3. PQR Whole angle

Congruence

• Two angles are congruent if they have the same measure If ABC PQR then mABC = mPQR

• Two segments are congruent if they have the same measure YZABthenYZABIf

•Congruence: Having the same size and shape

Protractor Postulate

• A protractor is used to measure angles

• Angles are measured using Degrees

Angle addition postulate

• If P is in the interior of RST then mRSP + mPST = m RST

RSP

PST

S

R•

•T

•P

RST

4 angle types

Acute Angle

0° < mA < 90 °

A

Right Angle

mA = 90 °

A

AObtuse Angle

90° < mA < 180 °

A•

Straight Angle

mA = 180 °

m TMF = m TMW + m WMF

m TMF = 27 + 63

m TMF = 90

m XLV = m XLC + m CLV

m XLV = 39 + 103

m XLV = 142

HW #5Pg 28: 1-39, 51-58, 64-73