Angles on opposite sides of a
transversal and outside the two lines it intersects.
Example
In these figures, angles 2 and 8 are alternate exterior angles.
When lines are parallel, such as lines
d and
e, the alternate exterior angles are congruent.
In the
figure on the right, angles 2 and 8 have the same measure, as lines
d and
e are parallel lines. These angles are
congruent.
