1. 3-1 DEFINITIONS Chapter 3 Test: Tuesday Oct. 18 th Quiz: Friday Oct. 14th

2. P ARALLEL L INES Coplanar lines that do not intersect Symbol: ||

3. S KEW L INES Non-coplanar lines Can they be parallel? NO! Definition of parallel is “coplanar” Can they intersect NO!

4. T OO What lines are parallel? What planes are parallel? What lines are skew? AB D C E H F G

5. T HEOREM If two parallel planes are cut by a third plane, then the lines of intersection are parallel. X Y Z A B C D If X||Y then AB||CD

6. T RANSVERSAL A line that intersects two or more coplanar lines in different points p is the transversal of m and n Exterior angles: 1,2,8,7 Interior angles: 4,3,5,6 Alternate Interior angles (AI): 4&6,3&5 Same-Side Interior angles (SSI): 4&5, 3&6 Corresponding angles (Corr): 1&5, 4&8, 2&6, 3&7 m n p 1 2 43 56 78

7. Ways To remember: Alt. Int. Angles make a big Z when you trace them. SSI angles make a “bracket” or “sandwich”. Corresponding angles must be in the same exact spot but on another pair of lines.

8. TOO Page 75 #2-9 Answers: 2) SSI 3) Corr. 4) None 5) Alt. Int. 6) None 7) Corr. 8) SSI 9) Alt. Int.

9. H OMEWORK 3.1 Definitions Worksheet Only do the problems that are numbered, some of the worksheet is notes