Notes for Section 1-4

Measuring Segments and Angles

To measure a segment, we can use a ruler and measure the distance between

the two ____________.

OR

We can think of the segment as part of a ___________ line.

A

- 4

B C D E F G H I

- 3 - 2 - 1 0 1 2 3 4

A

- 4

B C D E F G H I

- 3 - 2 - 1 0 1 2 3 4

Look at segment AE

How can we determine the

length of segment AE?

The coordinate of A is _______

The coordinate of E is _______

| | = | | =

A

- 4

B C D E F G H I

- 3 - 2 - 1 0 1 2 3 4

Congruent Segments

Two segments with the same ____, denoted __

Can you determine some congruent segments from the number line below?

Practice 1-4

# 4 - 7

An important postulate…….

If three points A, B, and C are _______ and B is between A and C, then ________________.

Practice 1-4

# 1 – 3, 9 - 11

MidpointA point that divides a

segment into two _________ segments.

A midpoint _____ the segment.

Let’s look at the following example.

Z is the midpoint of segment XY, and XY = 27.

Find XZ.

Practice 1-4

# 21 - 22

AngleFormed by two _____ with the same endpoint,

denoted ___

The endpoint is called the _____

of the angle.

A

BC

1

There are four ways to name

this angle.

__________________________

B

One way to express the

measure of an angle is in

_________.65°

We would write this as……

______________

Angle Measuring

Activity

Acute AngleAn angle with

measurement between ____ and ____ degrees.

Right AngleAn angle with

measurement of _____ degrees.

Obtuse AngleAn angle with

measurement between ____ and ___ degrees.

Straight AngleAn angle with

measurement of ____ degrees.

An important postulate……

If point B is in the ________ of AOC,

A

O C

B

then _________________________

Congruent AnglesAngles with the same ________.

For example…

If____________,

Then____________

Practice 1-4

# 8, 12 - 20