1. Properties of Parallel Lines
Geometry 3-1

2. Definition Transversal – A line that crosses two other lines
Note: the two other lines may be parallel, but do not need to be parallel
Definition

3. Corresponding Angles – Angles that appear in the same relative positionX X
Definition

4. Alternate Interior Angles – Angles between the pair of lines and on opposite sides of the transversal X X
Definition

5. Alternate Exterior Angles – Angles outside the pair of lines and on opposite sides of the transversal X X
Definition

6. Same Side Interior Angles – Angles inside the pair of lines and on the same side of the transversalX X
Definition

7. Transversal Same side of Transversal Opposite sides of Transversal
Between the Parallel Lines
Same Side Interior
Alternate Interior
Outside the Parallel Lines
Alternate Exterior
Same position compared to parallel lines
Corresponding

8. X X
Corresponding Angles

9. Consecutive Interior AnglesX X

10. Alternate Interior AnglesX X
Alternate Interior Angles

11. X X
Corresponding Angles

12. Alternate Exterior Angles

13. Consecutive Interior AnglesX X
Consecutive Interior Angles

14. Consecutive Interior AnglesX X
Consecutive Interior Angles

15. Alternate Interior AnglesX X
Alternate Interior Angles

16. Corresponding Angles X X

17. Alternate Interior AnglesX X
Alternate Interior Angles

18. Alternate Exterior Angles

19. Alternate Exterior Angles

20. Corresponding Angles X X

21. Alternate Exterior Angles

22. Corresponding Angles X X

23. X X
Corresponding Angles

24. Alternate Interior AnglesX X

25. X X
Corresponding Angles

26. Consecutive Interior AnglesX X

27. X X
Corresponding Angles

28. Alternate Interior AnglesX X

29. Consecutive Interior AnglesX X
Consecutive Interior Angles

30. Alternate Exterior Angles

31. X X
Corresponding Angles

32. Corresponding Angles X X

33. Investigation

34. Investigation

35. Investigation

36. Conjecture / Postulate
If two parallel lines are cut by a transversal, then the corresponding angles are congruent X X
Conjecture / Postulate

37. If two parallel lines are cut by a transversal, then the alternate interior angles are congruentX X
Conjecture / Theorem

38. If two parallel lines are cut by a transversal, then the alternate exterior angles are congruent
Conjecture / Theorem

39. If two parallel lines are cut by a transversal, then the same side interior angles are supplementaryX X
Conjecture / Theorem

40. Will these conjectures hold if the lines are not parallel?
Try it No
Investigation

41. Practice

42. Practice

43. Practice

44. Practice

45. Practice

46. Practice

47. Pages 119 – 121
10-18, 24, 29
Homework