http://www.ck12.org Chapter 3. Parallel and Perpendicular Lines
3.5 Alternate Exterior Angles
Here you’ll learn what alternate exterior angles are and their relationship with parallel lines.
What if you were presented with two angles that are on opposite sides of a transversal, but outside the lines? How
would you describe these angles and what could you conclude about their measures? After completing this Concept,
you’ll be able to answer these questions using your knowledge of alternate exterior angles.
Watch This
MEDIA
Click image to the left for more content.CK-12 Foundation: Chapter3AlternateExteriorAnglesA
Watch the portions of this video dealing with alternate exterior angles.
MEDIA
Click image to the left for more content.James Sousa:Angles and Transversals
MEDIA
Click image to the left for more content.James Sousa:Proof of Alternate ExteriorAngles Converse
Guidance
Alternate Exterior Anglesare two angles that are on theexterior oflandm, but on opposite sides of the transversal.
Alternate Exterior Angles Theorem:If two parallel lines are cut by a transversal, then the alternate exterior angles
are congruent.
The proof of this theorem is very similar to that of the Alternate Interior Angles Theorem.
Converse of the Alternate Exterior Angles Theorem:If two lines are cut by a transversal and the alternate exterior
angles are congruent, then the lines are parallel.