## Elementary Geometry for College Students (7th Edition)

1. given 2. Corresponding $\angle$s are $\cong$ 3. Vertical $\angle$s are $\cong$ 4. $\angle$ 3 $\cong$ $\angle$4 5.$\angle$ 1 $\cong$ $\angle$4
1. Given 2. If two parallel line l and m cut by transversal t, then corresponding angles of 1 and 2 are congruent 3. By theorem all vertical angles are congruent 5. By theorem of transitive, if $\angle$1 $\cong$ $\angle$ 2, then $\angle$2 $\cong$ $\angle$ 3 therefore $\angle$1 $\cong$ $\angle$ 3