(1, 5), (2, 7), (3, 10), (4, 12) solve for domain D={5, 7, 10, 12}

D={1, 2, 3, 4}

D={1, 5, 2, 7}

Cannot be determined

1. ∠1 is complementary to ∠2 and ∠3 is complementary to ∠2. subtraction property of equality 2. m∠1 + m∠2 = 90 and m∠3 + m∠2 = 90 substitution 3. m∠1 + m∠2 = m∠3 + m∠2 definition of complementary 4. m∠1 = m∠3 given