Additional Links

 Exterior Angle     Parallel Lines     Transversal  

Alternate Exterior Angles
Definition of Alternate Exterior Angles

• When two lines are cut by another line (transversal), the pairs of angles formed outside the two lines and on the opposite of the transversal are called Alternate Exterior Angles.

More about Alternate Exterior Angles

• If two parallel lines are cut by a transversal, the alternate exterior angles are congruent.

Example of Alternate Exterior Angles

• AB || CD and EF is the transversal cutting the parallel lines. So, ∠2 and ∠8, ∠1 and ∠7 are the pairs of alternate exterior angles in the figure shown.

Solved Example on Alternate Exterior Angles

PQ and RS are two lines and UT is a transversal of PQ and RS. Which among the following is a pair of alternate exterior angles?

Choices:
A. ∠4 and ∠5
B. ∠2 and ∠8
C. ∠1 and ∠2
D. ∠1 and ∠8
Correct Answer: D
Solution:
Step 1: When two lines are cut by another line (transversal), the pairs of angles formed outside the two lines and on the opposite of the transversal are called Alternate Exterior Angles.
Step 2: From the figure, PQ and RS are parallel lines and UT is a transversal passing through the parallel lines.
Step 3: The pairs of alternate exterior angles are
             ∠1 and ∠8
             ∠2 and ∠7
Step 4: Hence, ∠1 and ∠8 are the alternate exterior angles in the given figure.

Related Terms for Alternate Exterior Angles

• Exterior Angle
• Parallel Lines
• Transversal

Additional Links for Alternate Exterior Angles

• Click here for samples
• Back to Mathematics Dictionary