According to the Vertical Angles Conjecture, m∠1 and m∠3 are equal to each other. Knowing that corresponding angles ∠1 and ∠2 are congruent, then by Transitive Property of Equality, ∠2 and ∠3 are also congruent to each other. Therefore, alternating interior angles ∠2 and ∠3 have equal measures and are congruent.