1-3: Measuring Segments

Ruler Postulate• Every point on a line can be paired with a real

number. This makes a ____________ ___________________ between the points on the line and the real numbers. The real number that corresponds to a point is called the ____________ of the point.

one-to-onecorrespondence

coordinate

BA

What’s the distance between A and B?

3b1a

3 21

Distance Formula (on a number line)

• Take the absolute value of the difference of the coordinates of two points:

AB ba AB means the distance from A to B

Example 1: What is CD?B C D E

CD c d 2 10CD

8CD 8

10 2CD

8CD 8

2 10

• Postulate 1-6:• If three points A, B and C are collinear and B is

between A and C, then: AB

A CB

AB BC

AC

CB CA

Example 2: If LN=32, what are LM and MN?

L NM3 8x 2 4x

3 8 2 4 32x x 5 12 32x

5 20x 4x

3(4) 8LM 20

2(4) 4MN 12

Complete Got It? #2 p.21

42JK

78KL

Segment Addition Postulate

Vocabulary

• Congruent Segments• Two or more segments that have the same length• Symbol

• Midpoint• Point that divides a segment into two congruent

segments.

• Segment Bisector• Point, line, ray or other segment that intersects a

segment at its midpoint.• Divides segment into two equal length segments.

Example 3: is a segment bisector of . What are

A

R T

C

S

AC RT

, and ?RS ST RT

7 3x 3 1x

What do you know?

RS ST

How do you use

what you

know?

7 3 3 1x x

Solve 7 3 3 1x x 4 4x

1x

Substitute RS

ST

RT

4

4

8

7(1) 3

3(1) 1

4 4

Homework: p. 24 #’s 10-16, 19-22, 25-29, 39, 43, 48-56 even