Parallel Lines and Transversals

Section 3-1

2 lines that do not intersect are either parallel or skew.

Parallel lines ( lines) do not intersect and are coplanar.

Skew lines do not intersect and are not coplanar.

Parallel planes ( planes) do not intersect.

Plane X is parallel to plane YA line and a plane are parallel if

they do not intersect.X

Y

H G

DE

AB

CFEF plane Y

A transversal is a line that intersects 2 or more coplanar lines in different points.

1 23 4

5 67 8

transversal

interior

exterior

exterior

Alternate interior angles are 2 nonadjacent interior angles on opposite sides of the transversal.

1 23 4

5 67 8

63 and 54 and

Consecutive interior angles are 2 interior angles on the same side of the transversal.

1 23 4

5 67 8

53 and 64 and

Alternate exterior angles are 2 nonadjacent exterior angles on opposite sides of the transversal. 1 2

3 4

5 67 8

81 and 72 and

Consecutive exterior angles are 2 exterior angles on the same side of the transversal.

1 23 4

5 67 8

71 and 82 and

Corresponding angles are 2 angles in corresponding positions relative to the 2 lines.

1 23 4

5 67 8

73 and 84 and

62 and51 and

Joke TimeWhat did E.T.’s Mom say

when he got home?

Where on Earth have you been?

What happened when the pig pen broke?

The pigs had to use a pencil.