Measuring Segments

Bell Ringer

1.2

Measuring Segments

Objective: Students will be able to find segment measures

Definitions/Postulates

Postulate
- AKA “axiom”
- a rule that is accepted without proof

Ruler Postulate
The points on a line can be matched one
to one with the real numbers. The real
number that corresponds to a point is
the coordinate of the point.

The distance between points A and B,
written as AB, is the absolute value
of the difference of the coordinates A and B.

Example 1 - Measuring Segments

a.

Use the diagram and the ruler postulate to determine the length of the segment.

Example 1 - Measuring Segments

Use a ruler to determine the length of the segment.

a.

b.

c. d.

Definitions/Postulates

Congruent Segments

-Definition: Line segments that have the same length

-Phrasing:

-The length of

is equal to length of

OR

- is congruent to

-A tick mark is used to show congruent segments in a diagram.

Lengths are equal.

Segments are congruent.

“is equal to”

“is congruent to”

Example 2 - Comparing Segments for Congruence

a.

Plot the following points in the coordinate plane. Then determine if and are congruent.

Example 2 - Comparing Segments for Congruence

b. Plot the following points in the coordinate plane. Then determine if and are congruent.

Definitions/Postulates

When three points are collinear, you can say that one point is between the

other two.

Point B is between

points A and C.

Point E is not between

points D and F.

Definitions/Postulates

Segment Addition Postulate

If B is between A and C, then

.

If

, then B is between A and C.

Example 3 - Using the Segment Addition Postulate
**C is the question on the next slide**

a.

Find DF.

b. Find GH.

c. Find KL.

Example 3 - Using the Segment Addition Postulate

a.

Find DF.

b. Find GH.

c. Find KL.

Example 4 - Using the Segment Addition Postulate
**B is next quiz question*

a. The cities shown on the map lie
approximately in a straight line. Find the
distance from Tulsa, OK, to St. Louis, MO.

b. The cities shown on the map lie
approximately in a straight line. Find the
distance from Albuquerque, NM, to Provo,
UT.

Example 4 - Using the Segment Addition Postulate
**B is next quiz question*

a. The cities shown on the map lie
approximately in a straight line. Find the
distance from Tulsa, OK, to St. Louis, MO.

b. The cities shown on the map lie
approximately in a straight line. Find the
distance from Albuquerque, NM, to Provo,
UT.