Step 2: Determine the relationship between angles 1 and 2, and angles 3 and 4
Angles 1 and 2 are supplementary angles, as are angles 3 and 4. Therefore, m∠1 + m∠2 = 180° and m∠3 + m∠4 = 180°.
Step 3: Show congruence between angles 2 and 3
Since ∠1 ≅ ∠4, their measures are equal. We can substitute m∠4 for m∠1 in the equation m∠1 + m∠2 = 180°. This gives us m∠4 + m∠2 = 180°. We also know m∠3 + m∠4 = 180°. Since both m∠2 and m∠3 sum to 180° when added to m∠4, m∠2 must equal m∠3. Therefore, ∠2 ≅ ∠3.