While standing on a roof, you drop a hammer. the function y=16-16t^2
represents the height y (in feet) of the hammer t seconds after it is dropped. after how many seconds does the hammer land on the ground?

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