3.6 Parallel Lines Cut by a Transversal

Vocabulary

Supplementary: angles that add up to 180°

100°

80°

Linear Pairs are supplementary but
supplementary angles aren’t always a
linear pair.

​80°

​100°

Vocabulary

Transversal: A line that intersects two or
other lines at different points

Parallel Lines: lines on the same plane that
never intersect

Vocabulary
Interior:

​In between the parallel lines

Vocabulary
Exterior:

​Outside the parallel lines

Same-Side Interior

1

2

3

4

5

6

7

8

∡3 & ∡5

∡4 & ∡6

​Same side of transversal, between the parallel lines

Same-Side Exterior

1

2

3

4

5

6

7

8

∡1 & ∡7

∡2 & ∡8

​Same side of transversal, outside the parallel lines

Alternate Interior

1

2

3

4

5

6

7

8

∡3 & ∡6

∡4 & ∡5

​Opposite sides of transversal, between the parallel lines

Alternate Exterior

1

2

3

4

5

6

7

8

∡1 & ∡8

∡2 & ∡7

​​Opposite sides of transversal, outside the parallel lines

Corresponding

1

2

3

4

5

6

7

8

∡1 & ∡5

∡3 & ∡7

​Angles in the same relative postion. (i.e. both left of transversal and both on top of parallel line)

Angle Pairs Relationships

Alternate Interior

Alternate Exterior

Corresponding

Congruent

Supplementary

Same-Side Interior

Same-Side Exterior

​(Same Size)

​(Add to =180)