1. 3-1 Lines and Angles

2. Parallel and Skew Parallel lines are coplanar lines that do not intersect. – The symbol  means “is parallel to”. Skew lines are noncoplanar; they are not parallel and do not intersect. Parallel planes are planes that do not intersect. – A line and a plane can be parallel; segments and rays can be parallel or skew.

3. Identifying Nonintersecting Lines and Planes  Which segments are parallel to AB?  Which segments are skew to CD?  What are two pairs of parallel planes?  What are two segments parallel to plane BCGF?  Why are FE and CD not skew?

4. Angles Pairs Formed by Transversals A transversal is a line that intersects two or more coplanar lines at different points (line t). Two angles are corresponding angles if they occupy corresponding positions (1 and 5, 3 and 7, 2 and 6, 4 and 8). Two angles are alternate exterior angles if they lie outside the two lines on opposite sides of the transversal (1 and 8, 2 and 7). Two angles are alternate interior angles if they lie between the two lines on opposite sides of the transversal (3 and 6, 4 and 5). Two angles are consecutive (or same side) interior angles if they lie between the two lines on the same side of the transversal (3 and 5, 4 and 6). tt 12 34 56 78 12 34 56 78 12 34 56 78 12 34 56 78 12 34 56 78

5. Identifying an Angle Pair  Identify all pairs of angles with the following relationships: – Alternate interior – Same-side interior – Corresponding – Alternate exterior