## Elementary Geometry for College Students (6th Edition)

1. Both $\angle 1$ and $\angle 2$ are right angles. 2. By definition $m\angle 1 = 90^{\circ}$, $m\angle 2 =90^{\circ}$ 3. $m\angle1=m\angle2$ 4. If two angles have the same angle measure, they are congruent. Therefore, $\angle1\cong\angle2$.