Bellwork 4 Suppose you know PQ and QR

Bellwork 4) Suppose you know PQ and QR. Can you use the segment addition postulate to find PR? Explain.

1 -3 Measuring Segments and Angles

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.

Ruler post. (continued) A B x 1 x 2 • The length of AB can be found by x 2 -x 1 • **The symbol for the length of AB is AB.

Example: Find AB. A Point A is at 1. 5 and B is at 5. So, AB = 5 - 1. 5 = 3. 5 B

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

Post. 1 -6: Segment Addition Post. • If B is between A & C, then AB + BC = AC. • If AB + BC = AC, then B is between A & C. A B C

EX. • If EG= 59, what are EF and FG? E 8 x-14 F 4 x+1 G

OYO. • If EG= 120, what are EF and FG? E 4 x+6 F 7 x+15 G

Ex: if DE=2, EF=5, and DE=FG, find FG, DF, DG, & EG. D E F FG=2 DF=7 DG=9 EG=7 G

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

• Midpoint- a point that divides the segment into two congruent segments • Segment Bisector- a point, line, or ray that intersects a segment at its midpoint

Ex. . • Q is the midpoint of PR. What are PQ, QR, and PR? P 6 x-7 Q 5 x +1 R