1. Transversal: A line that intersects two coplanar lines1 2 3 4 5 6 7 8
Eight angles are formed
 Classify as:
Interior
Exterior

2. Transversal: A line that intersects two coplanar lines1 2 3 4 5 6 7 8

3. Exploring Parallel Lines

4. Vertical Angles
The two angles in red are vertical angles, they are congruent.
The two angles in yellow are vertical angles, they are congruent.

5. Angles and parallel lines.
The angles in red are all equal in size.
The angles in yellow are all equal in size.

6. Angles and parallel lines.
* All the acute angles are congruent
* All the obtuse angles are equal.
Some of these angles have special names.

7. Corresponding Angles

8. Corresponding Angles are equal.

9. You can spot corresponding angles by looking for the following shapes

10. You can spot corresponding angles by looking for the following shapes

11. Corresponding Angles: ‘F’ shape

12. Alternate angles

13. Alternate angles are equal

14. You can spot alternate angles by looking for the following shapes

15. Alternate Angles: ‘Z’ shape

16. Interior Angles add to 180⁰

17. Interior Angles add to 180⁰
Angles and parallel lines.
Interior Angles
Interior Angles add to 180⁰

18. You can spot interior angles by looking for the following shapes

19. Interior Angles: ‘C’ shape

20. Work out the value of the angles x and y in the diagram below.
Using the opposite angle rule, y and 60 are equal
Using the alternate angle rule, y and x are equal

21. Work out the value of the angles x and y in the diagram below.
Using the corresponding angle rule, y and 125 are equal
Using the straight angle rule,

22. Work out the value of the angles x and y in the diagram below.
Using the interior angle rule, the angles shown add to 180⁰.
So the angle in red is 55⁰.
Using the opposite angle rule,
Using the corresponding angle rule,

23. Work out the value of the angle p in the diagram below.
The angles shown are corresponding angles.
Using the opposite angle rule,

24. Sample problem: the line L is parallel to side rs of the triangle, work out the angles x and y.
Step1: As rs and L are parallel, we can use the alternate angle rule:
Step2: Triangle rule: