1. 1. Construct a geometry ruler 2. Define length and congruent 3. Identify and use the Segment Addition Postulate

2. In defining the length of a segment, we will use a number line, which is like a ruler. A number line is a line that has been set up to correspond with the real numbers

3. Definition: Length of Let A and B be points on a number line, with coordinates a and b. Then the measure of which is called its length, is |a – b| or |b – a| A B m, or AB = 7 |-6 -1| or |1 –(-6)|

4. The Real Number Line negative numbers are to the left of 0 positive numbers are to the right of 0 a < b is read "a is less than b" and means a is further to the left on the number line than b a > b is read "a is greater than b" and means a is further to the right on the number line than b a > 0 means a is positivea < 0 means a is negative

5. If we want to know how far apart points on the number line are, we can take the difference between them and then take the absolute value. 2-7-6-5-4-3-21573 0468 8 units apart What is the distance from -5 to 3?

6. A XB Find the measures (lengths of on the number line above.

7. Congruent figures are figures that are the same size and shape. If your move one of them onto the other, they will match exactly, like the figures below.

8. The symbol for congruence is Is read as “Segment is congruent to segment.” In geometry, tick marks are used to show which segments are known to be congruent. Within a given illustration, segments that have a single tick mark are congruent. Similarly, segments that have two tick marks are congruent, and so on.

9. Segment Congruence Postulate If two segments have the same length as measured by a fair ruler, then the segments are congruent. Also, if two segments are congruent, then they have the same length as measured by a fair ruler.