# Warm-Up: Billiards (“Pool”) - PowerPoint PPT Presentation

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Warm-Up: Billiards (“Pool”). Who has played pool? What’s a “bank shot”? How do you know where to hit the ball on the side? It’s all in the angles! Angles are the foundation of geometry. 1.4 Angles & their Measures. Objectives: Define: Angle, side, vertex, measure, degree, congruent

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Warm-Up: Billiards (“Pool”)

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### Warm-Up: Billiards (“Pool”)

• Who has played pool?

• What’s a “bank shot”?

• How do you know where to hit the ball on

• the side?

• It’s all in the angles!

• Angles are the foundation of geometry

## 1.4 Angles & their Measures

Objectives:

Define: Angle, side, vertex, measure, degree, congruent

Name angles with the vertex always in the middle

Measure angles with a protractor

Identify congruent angles

Classify angles as acute, right, obtuse, or straight

### Angle symbol:

• 2 rays that share the same endpoint (or initial point)

Sides – the rays XY & XZ

Vertex – the common endpoint; X

Y

X

5

Z

Named <YXZ, <ZXY (vertex is always in the middle), or <X (if it’s the only <X in the diagram).

Angles can also be named by a #. (<5)

In the figure, there are three different <Q’s (two smaller ones and a larger one). therefore, none of them should be called <B. The vertex is ALWAYS in the middle of the name

One angle only:

< EFG or < GFE

Three angles:

< ABC or < CBA

< CBD or < DBC

< ABD or < DBA

### Postulate 3: Protractor Post.

• The rays of an angle can be matched up with real #s (from 1 to 180) on a protractor so that the measure of the < equals the absolute value of the difference of the 2 #s.

55o

20o

m<A = 55-20

= 35o

B is ___________

C is ___________

D is ___________

### Interior or Exterior?

in the interior

in the exterior

on the <

B

C

D

A

• 2 angles that share a common vertex & side, but have no common interior parts.

(they have the same vertex, but don’t overlap) such as <1 & <2

2

1

### Example 2:

m < FJH = m < FJG + m < GJH

m < FJH = 35° + 60°

### Example 3:

.

If m<QRP=5xo, m<PRS=2xo, & m<QRS=84o, find x.

5x+2x=84

7x=84

x=12

m<QRP=60o m<PRS=24o

S

P

Q

R

Acute angle –

Right angle –

Obtuse angle –

Straight angle –

Measures between 0o & 90o

Measures exactly 90o

Measures between 90o & 180o

Measures exactly 180o

### Example 4: Classifying Angles

• A. straight

• B. acute

• C. obtuse

Name an acute angle

<3, <2, <SBT, or <TBC

Name an obtuse angle

<ABT

Name a right angle

<1, <ABS, or <SBC

Name a straight angle

<ABC

S

T

3

1

2

A

B

C