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1.3 a: Angles, Rays, Angle Addition, Angle Relationships PowerPoint Presentation

1.3 a: Angles, Rays, Angle Addition, Angle Relationships

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1.3 a: Angles, Rays, Angle Addition, Angle Relationships. CCSS.

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1.3 a: Angles, Rays, Angle Addition,

Angle Relationships

CCSS

G-CO.9 Prove theorems about lines and angles. Theorems include: vertical angles are congruent; when a transversal crosses parallel lines, alternate interior angles are congruent and corresponding angles are congruent; points on a perpendicular bisector of a line segment are exactly those equidistant from the segment’s endpoints.

Rays

- A ray extends forever in one direction
- Has one endpoint
- The endpoint is used first when naming the ray

B

B

B

B

ray RB

R

R

R

R

R

T

ray WT

W

Angles

- Angles are formed by 2 non-collinear rays
- The sides of the angle are the two rays
- The vertex is where the two rays meet

Vertex- where they met

ray

ray

Angles (cont.)

- Measured in degrees
- Congruent angles have the same measure

Naming an Angle

You can name an angle by specifying three points: two on the rays and one at the vertex.

- The angle below may be specified as angle ABC or ABC. The vertex point is always given in the middle.

- Named:
- Angle ABC
- Angle CBA
- Angle B * *you can only use the
- vertex if there is ONE
- angle

Vertex

Ex. of naming an angle

- Name the vertex and sides of 4, and give all possible names for 4.

T

Vertex:

Sides:

Names:

X

XW & XT

WXT

TXW

4

4 5

W X Z

Angles can be classified by their measures

- Right Angles – 90 degrees
- Acute Angles – less than 90 degrees
- Obtuse Angles – more than 90, less than 180

Example of Angle Addition Postulate

100

Ans: x+40 + 3x-20 = 8x-60

4x + 20 = 8x – 60

80 = 4x

20 = x

40

60

Angle PRQ = 20+40 = 60

Angle QRS = 3(20) -20 = 40

Angle PRS = 8 (20)-60 = 100

Types of Angle Relationships

- Adjacent Angles
- Vertical Angles
- Linear Pairs
- Supplementary Angles
- Complementary Angles

2)Vertical Angles

- Vertical Angles - 2 non-adjacent angles formed by 2 intersecting lines (across from each other). They are CONGRUENT !!

1

2

3) Linear Pair

- Linear Pairs – adjacent angles that form a straight line. Create a 180o angle/straight angle.

2

1

3

4) Supplementary Angles

- Supplementary Angles – two angles that add up to 180o (the sum of the 2 angles is 180)

Are they different from linear pairs?

5) Complementary Angles

- Complementary Angles – the sum of the 2 angles is 90o

Angle Bisector

- A ray that divides an angle into 2 congruent adjacent angles.
BD is an angle bisector of <ABC.

A

D

B

C

Last example: Solve for x.

BD bisects ABC

A

D

x+40o

x+40=3x-20

40=2x-20

60=2x

30=x

3x-20o

C

B

Why wouldn’t the Angle Addition Postulate help us solve this initially?

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