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

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

2. 3; AB, AC, BC 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. Learn to classify pairs of lines.

4. Vocabulary parallel lines perpendicular lines skew lines

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

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

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

8. 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.

9. 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.

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

11. 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.

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

13. 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.

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

15. 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.

16. 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.

17. 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