Definition of TransversalIn a plane, a line is a transversal if and only if it intersects two or more lines, each at a different point. When transversal intersect two lines, eight angles are formed.

Interior Angles- lie between the two lines

Exterior Angles- lie outside the two lines

Alternate Interior Angles- interior angles

on opposite sides of the transversal

Consecutive Interior Angles-interior angles

on the same side of the transversal.

Alternate Exterior Angles- exterior angles

on the opposite sides of the transversal.

These angles are given special names:

When a transversal cuts two parallel lines, then following theorems apply:

Theorem 4-1 Alternate Interior Angles Thm.If two parallel lines are cut by a transversal, then each pair of alternate interior angles is congruent.

4-2 Parallel Lines and TransversalsTuesday, October 22, 2013

9:49 PM

Chapter 4 Page 1

Theorem 4-2 Consecutive Interior Angles Thm.If two parallel lines are cut by a transversal, then each pair of consecutive interior angles is supplementary.

Theorem 4-3 Alternate Exterior Angles ThmIf two parallel lines are cut by a transversal, then each pair of alternate exterior angles is congruent.

Ex. 1 Identify each pair of angles.

a) 3 and 5

b) 1 and 8

Ex. 2

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Ex. 3

Ex. 4

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