[tex]\begin{gathered} \angle1\text{ and }\angle2\text{ are right angles. }\; \; \; \text{Given} \\ m\angle1=90\degree,m\angle2=90\degree,\text{ }\; \; \; \text{Definition of a right angle} \\ m\angle1=m\angle2,\; \; \; \; \text{Substitution property of equality} \\ \angle1\cong\angle2,\; \; \; \; \text{Definition of angle congruence} \end{gathered}[/tex]
