1. Measuring and Constructing Line Segments
Chapter 1.2

2. Today’s lesson: fancy terms for very un-fancy things
Postulate : A rule that is accepted without proof
Examples:
Through any two points, there is exactly one line.
If two lines intersect, their intersection is exactly one point.
A plane contains at least 3 non-collinear points

3. Fancy terms for very un-fancy things
Points on a line can be matched 1 to 1 with real numbers. The real number that corresponds to a point is called a coordinate.
Ruler Postulate : J K
What it actually means:
The coordinate of point J is -4
The coordinate of point K is 3

4. Fancy terms for very un-fancy things
The distance between points A and B is written as AB. Distance is the absolute value of the difference of coordinates A and B
Ruler Postulate (cont’d) :
What it actually means:
ST = | 5.4 – 2 | = 3.4 inches

5. Segments are congruent.
Fancy terms for very un-fancy things
Congruent segments:
Line segments that have the same length
Lengths are equal.
AB = CD
Segments are congruent.
AB CD

6. Fancy terms for very un-fancy things
Segment Addition Postulate
If B is between A and C, then AB + BC = AC
What it actually means: