1. 1.3 Segments & their Measures

2. Postulates
Rules that are accepted as true without having to be proven.
Sometimes they are called axioms.

3. Postulate 1: Ruler post.
The points on a line can be matched with those on the real # line.
The real # that corresponds to a point is the coordinate of the point.
If you find the difference between the coordinates of 2 points, then take the absolute value, you will have the distance between the points.

4. Ruler post. (continued)A B x1 x2
The length of AB can be found by x2-x1
**The symbol for the length of AB is AB.

5. Example: Find AB. A B Point A is at 1.5 and B is at 5.
So, AB = = 3.5

6. Is Alex between Ty and Josh?
Yes! Ty
Alex
Josh
No, but why not?
How about now?
In order for a point to be between 2 others, all 3 points MUST BE collinear!!

7. Post. 2: Segment Addition Post.
If B is between A & C, then
AB + BC = AC.
If AB + BC = AC, then B is between A & C. C B A

8. Ex: if DE=2, EF=5, and DE=FG, find FG, DF, DG, & EG.

9. (x1,y1) & (x2,y2) are the 2 points.
Reminders:
Pythagorean Theorem –
a2+b2=c2
a & b are the lengths of the legs of a right triangle and c is the length of the hypotenuse.
Distance formula –
(x1,y1) & (x2,y2) are the 2 points.

10. Segments that have the same length. If AB & XY have the same length,
Congruent ( ) Segments
Segments that have the same length.
If AB & XY have the same length,
Then AB=XY,
but
AB XY
Symbol for congruent

11. Assignment Packet Practice 1.3 odd