## Thinking Mathematically (6th Edition)

$m\angle{1} = 50^o \\m\angle{2} = 90^o \\m\angle{3}=50^o$
The right angle and angle 2 are vertical angles. This means that they have the same measurements. Thus, $m\angle{2} = 90^o$. The 40-degree angle and angle 1 are complementary angles, so their sum is 90 degrees. Thus, $m\angle{1}=90^o-40^o \\m\angle{1}=40^o$ Angles 1 and 3 are vertical angles, so their measurements are the same. Thus, $m\angle{3} = m\angle{1} = 50^o$