6th Grade Math Textbook, Fundamentals

 &KDSWHU

9-4

A is a line that intersects two or more

lines at different points. When a pair of parallel

lines is intersected by a transversal, eight angles

are formed. These angles form certain special

angle pairs.

In the figure, ABand CDare parallel lines and

are intersected by transversal t.

3, 4, 5, and 6 are because

they are inside the two parallel lines.

1, 2, 7, and 8 are because

they are outside the two parallel lines.

are pairs of nonadjacent

angles, one interior and one exterior, that are

both on the same sideof the transversal.

Corresponding angles formed by parallel lines

are congruent.

are a pair of nonadjacent

interior angles on opposite sidesof the transversal.

Alternate interior angles formed by parallel lines

are congruent.

are a pair of nonadjacent

exterior angles on opposite sidesof the transversal.

Alternate exterior angles formed by parallel lines

are congruent.

The map of Washington, D.C. above shows that the numbered streets are parallel

to one another. The numbered streets shown on this map are intersected

by Pennsylvania Avenue. The angles formed by the intersection of Pennsylvania

Avenue with 20th Street and with 22nd Street (shown in red on the map) are

congruent because they are corresponding angles. Similar results could be found

for the angles formed by the intersection of Pennsylvania Avenue with 18th Street,

with 19th Street, and with 21st Street.

Alternate exterior angles

Alternate interior angles

Corresponding angles

exterior angles

interior angles

transversal

Parallel Lines and Transversals

Objective To identify the kinds of angles formed when a pair of parallel lines is

intersected by a transversal• To use the properties of angle pairs and parallel lines

to find missing angle measures

The grid of streets in many cities consists of parallel
and intersecting lines. The map at the right shows
some of the streets in Washington, D.C. What kinds
of angles are formed whenever two parallel streets
are intersected by a third street?

AB

CD

43

21

8 7

65

t

Remember:Parallel lines are in the same

plane and do not intersect.

Corresponding angles:

1 and  5  1  5

2 and  6  2  6

3 and  7  3  7

4 and  8  4  8

Alternate interior angles:

3 and  6  3  6

4 and  5  4  5

Alternate exterior angles:

1 and  8  1  8

2 and  7  2  7

ABCD