1. Segments, Rays, Parallel Lines, and Planes Objectives: Define line segments and rays Properly name line segments and rays Identify parallel lines and skew lines

2. Line Segments A line segment is part of a line containing two endpoints and all points between them. Unlike lines, which extend forever in both directions, line segments have a definite beginning and end A line segment is named with the endpoints A B AB or BA

3. Rays A ray is part of a line that consists of one endpoint and all points of the line extending in one direction Name a ray using the endpoint first and then another point on the ray When naming, make sure the arrow points away from the endpoint. A B AB NOT BA

4. Rays, continued Are these two rays the same? A B A B No Different endpoints Extend in different directions BA AB

5. Opposite Rays Are two collinear rays with the same endpoint Always form a line J K L KJ and KL are opposite rays

6. Parallel Lines Lines that Never intersect Extend in the same directions Coplanar

7. Skew lines Lines that: Never intersect Are non-coplanar Extend in different directions

8. Parallel Planes Parallel planes are planes that never intersect Example: the purple planes in the above illustration A line and plane that never intersect are also parallel

9. Learning Check and Summary Which of the following has no endpoints? Ray, Line Segment, Line Which of the following has two endpoints? Ray, Line Segment, Line Which of the following has one endpoint and extends in one direction? Ray, Line Segment, Line Which of the following extend in the same direction? Parallel lines, skew lines Which of the following extend in different directions? Parallel lines, skew lines

10. Exercises P. 13-15 All P. 253 All P. 255 All 10