1. ∠1 and ∠2 are comp.
1. given
2. ∠3 and ∠4 are comp.
2. given
3. ∠2 ≅ ∠4
3. given
4. m∠1 + m∠2 = 90° m∠3 + m∠4 = 90°
4. def. of complementary angles
5. m∠2 = m∠4
5. def. of congruent ∠s
6. m∠1 + m∠2 = m∠3 + m∠4
6. substitution property
7. m∠1 = m∠3
7. subtraction property
8. ∠1 ≅ ∠3
8. def. of congruent ∠s