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Alternate Exterior Angles Theorem
See It in Action
Two examples of the idea done right—and one common look-alike that is not right.
EXAMPLE
EXAMPLE
NON-EXAMPLE
Definition
The Alternate Exterior Angles Theorem states:
“If two parallel lines are cut by a transversal, then each pair of alternate exterior angles is congruent.”
In simple terms:
When a transversal crosses two parallel lines,
The alternate exterior angles (on opposite sides of the transversal and outside the parallel lines)
Will always be equal in measure.
Example:
If line l || m, and transversal t intersects them, then:
Angle 1 and angle 2 form a pair of alternate exterior angles, and angle 1 ≅ angle 2.
Video
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