1. Do now: Geo-Activity on page 53
Homework:
1.) 2.1 Practice B Worksheet
2.) 2.1 to 2.3 vocabulary due Monday
Objective: Bisect a segment Find coordinates of the midpoint of segment

2. Important Terms
Midpoint: The midpoint of a segment is the point on the segment that divides it into two congruent segments.
Segment bisector: A segment bisector is a segment, ray, line or plane that intersects a segment at its midpoint
Bisect: to bisect means to divide the segment into two congruent segments.

3. Example 1 Find segment lengths
M is the midpoint of AB. Find AM and MB.
A M B 26

4. Solution
M is the midpoint of AB, so AM is half of AB.

5. Example 2 Find segment lengths
P is the midpoint of RS. Find PS and RS.
R P S 7

6. Solution P is the midpoint of RS, so PS = RP = 7.
You know that RS is twice RP.
RS = 2 (RP) = 2 (7) = 14
Answer PS = 7 and RS = 14.

7. Follow-up
How are Examples 1 and 2 different?

8. Solution
Example 1 gives the length of the whole segment, and the length of half of the segment needs to be calculated. Example 2 gives the length of half of the segment, and the length of the whole segment needs to be calculated.

9. Checkpoint
Find DE and EF.
Find NO and MO.
D E F 18
M N O 11

10. Solution
DE = 9
EF = 9
NO = 11
MO = 22

11. Example 3 Use algebra with segment lengths
Line l is a segment bisector of AB. Find the value of x.
DRAW IN VISUAL

12. Solution M is midpoint, so write an equation.
Substitute values for AM and MB.
Solve for x.

13. The Midpoint Formula
Words: The coordinates of the midpoint of AB are the averages of the x-coordinates and the y-coordinates of endpoints.
Symbols: The midpoint of the segment joining A(x1,x2) and B(x2,y2) is
Midpoint Formula: DRAW IN IMAGE

14. Example 4 Use the midpoint formula
Find the coordinated of the midpoint AB for A(1,2) and B(7,4).
DRAW IN VISUAL

15. Solution
DRAW VISUAL

16. CLOSING
Exit card
Based on the vocabulary that you learned, discuss how the terms midpoint, segment bisector, and bisect are related and fill out the exit card.