Unit 8.3
Perpendicular Bisectors
Study pages 306 ­ 308
1
Bisector ­ a line that divides a line segment into two equal parts.
Bisector
5 cm
5 cm
2
Midpoint ­ the point that divides a line segment into two equal parts.
Midpoint
5 cm
5 cm
3
Perpendicular bisector ­ line that divides a line segment into two equal parts at a 90 degree angle.
4 cm
4 cm
4
Using a triangle and ruler:
5
Using a triangle and ruler:
Step 1:
using a ruler, measure the line segment and mark the midpoint.
6
Using a triangle and ruler:
Step 2: Line up the triangle and draw a line at the edge which is 90o from the line at the midpoint.
7
Using a ruler:
8
Using a ruler:
Step 1:
9
Using a ruler:
Step 2:
10
Using a ruler:
Step 3:
11
Using a ruler:
This line is perpendicular to the original line segment (black).
12
Using Protractor and Ruler:
Step 1: Using a ruler, measure and mark the midpoint.
13
Using Protractor and Ruler:
Step 2: Line up the protractor with the midpoint and draw a point at the 900 mark.
14
Using Protractor and Ruler:
Step 3: Using a ruler, connect the points.
15
Using Protractor and Ruler:
This line is perpendicular to the original line segment (black).
16
Using a Compass and ruler:
17
Using a Compass and ruler:
18
Using a Compass and ruler:
Step 2: Do NOT adjust the compass.
Move the needle point to the other end of the line segment and draw another circle.
19
Using a Compass and ruler:
Step 3: Using a ruler, connect the two points at which the two circles intersect.
20
To check that the perpendicular bisector has been drawn correctly:
• Using a ruler, measure the two parts of the line segment to check that they are equal and • using a protractor, measure the angles to check each is 90o.
21
Do page 308­309 #1, 3­5
22