Which theorem states that alternate exterior angles are congruent when two lines are parallel?

Which theorem states that alternate exterior angles are congruent when two lines are parallel?

• A. Corresponding Angles Theorem
• B. Interiors on Same Side Theorem
• C. Alternate Exterior Angles Theorem
• D. Alternate Interior Angles Theorem

Answer: (C)

When two parallel lines are cut by a transversal, certain angle pairs are guaranteed to match. The angles that lie outside the two lines and on opposite sides of the transversal are congruent by this rule. This is exactly the Alternate Exterior Angles Theorem, which states that those two exterior angles are equal when the lines are parallel. This directly explains why those particular angles must have the same measure, and it distinguishes this relationship from other angle rules like corresponding angles or alternate interior angles, which describe different pairs of angles.

When two parallel lines are cut by a transversal, certain angle pairs are guaranteed to match. The angles that lie outside the two lines and on opposite sides of the transversal are congruent by this rule. This is exactly the Alternate Exterior Angles Theorem, which states that those two exterior angles are equal when the lines are parallel. This directly explains why those particular angles must have the same measure, and it distinguishes this relationship from other angle rules like corresponding angles or alternate interior angles, which describe different pairs of angles.