1. 8-4 Classifying Lines Warm Up Problem of the Day Lesson Presentation
Course 1
Warm Up
Problem of the Day
Lesson Presentation

2. Warm Up
Give the complement of each angle.
1. 80°
2. 64°
3. 15°
4. 48°
10°
26°
75°
42°

3. Problem of the Day
Draw three points that are not in a straight line. Label them A, B, and C. How many different lines can you draw that contain two of the points? Name the lines.
3; AB, AC, BC

4. Learn to classify the different types of lines.

5. Vocabulary
parallel lines
perpendicular lines
skew lines

6. Intersecting lines are lines that cross at one common point. Y W Z X
Intersecting lines are lines that cross at one common point.
Line YZ intersects line WX.
YZ intersects WX. B A M L
Parallel lines are lines in the same plane that never intersect.
Line AB is parallel to line ML.
AB ML.
The red arrows on the lines show that the lines are parallel.
Reading Math

7. S R T U
Perpendicular lines intersect to form 90° angles, or right angles.
Line RS is perpendicular to line TU.
RS TU.
Skew lines are lines that lie in different planes. They are neither parallel nor intersecting.
Line AB and line ML are skew.
AB and ML are skew. M L A B

8. Additional Example 1A: Classifying Pairs of Lines
Classify each pair of lines.
The lines intersect to form right angles.
They are perpendicular.

9. Additional Example 1B: Classifying Pairs of Lines
Classify each pair of lines.
The lines are in different planes and are not parallel or intersecting.
They are skew.

10. Additional Example 1C: Classifying Pairs of Lines
Classify each pair of lines.
The lines are in the same plane. They do not appear to intersect.
They are parallel.

11. Additional Example 1D: Classifying Pairs of Lines
Classify each pair of lines.
The lines cross at one common point.
They are intersecting.

12. Check It Out: Example 1A
Classify each pair of lines.
The lines are in the same plane. They do not appear to intersect.
They are parallel.

13. Check It Out: Example 1B
Classify each pair of lines.
The lines intersect to form right angles.
They are perpendicular.

14. Check It Out: Example 1C
Classify each pair of lines.
The lines are in different planes and are not parallel or intersecting.
They are skew.

15. Check It Out: Example 1D
Classify each pair of lines.
The lines cross at one common point.
They are intersecting.

16. Additional Example 2: Application
The handrails on an escalator are in the same plane. What type of line relationship do they represent?
The handrails are in the same plane and do not intersect.
The lines are parallel.

17. Check It Out: Example 2
The roads are in the same plane. What type of line relationship do they represent?
The lines cross at one common point.
The lines are intersecting.

18. Lesson Quiz
1. Sketch a pair of perpendicular lines.
2. Sketch a pair of parallel lines.
Use the figure to classify the lines.
3. AD and BC
4. AD and CF
5. AB and BG
parallel
skew
perpendicular