Parallel lines and planes are coplanar and do not intersect. Skew lines are noncoplanar and do not intersect. If two parallel planes are cut by a third plane, the lines of intersection will be parallel. A transversal is a line that intersects two or more coplanar lines. Alternate interior angles and same side interior angles are pairs of angles related to a transversal. Corresponding angles are in corresponding positions relative to two lines.

1. Parallel lines and planes 3-1

2. Parallel Lines Coplanar Don’t intersect

3. Skew Lines Noncoplanar Don’t intersect

4. Segments and rays can be parallel or skew

5. Parallel Planes (Which planes are parallel?)

6. Theorem 3-1 If 2 parallel planes are cut by a third plane, then the lines of intersection are parallel.

7. Transversal A line that intersects two or more coplanar lines Transversal

8. Alternate interior angles Two nonadjacent interior angles on opp. Sides of the transversal 3 and 6 4 and 5

9. Same side interior angles Two interior angles on the same side of the transversal 4 and 6 3 and 5

10. Corresponding angles Two angles in corresponding position relative to the two lines 2 and 6 1 and 5 3 and 7 4 and 8

11. Time to see what you learned…

12. Which lines are skew? AB and CD EF and HG HE and AD AB and DH BD and EH A B C D E F G H 0 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

13. Which angle is the same side interior angle to D? A E F H C A B C D E F G H 0 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

14. Which angle is the alternate interior angle to D? A E F H C A B C D E F G H 0 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

15. Which angle is the corresponding angle to C? A E F H G A B C D E F G H 0 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

16. SPICSA Page 76 2,4,6,12,14,16 Page 77 24,26,28,30,32,34