1. RW ≅ WT; UW ≅ WS
1. given
2. ∠SWR and ∠UWT are vertical angles
2. def. of vertical angles
3. ∠SWR ≅ ∠UWT
3. ♣
4. △SWR ≅ △UWT
4. ♦
5. ∠WRS ≅ ∠WTU, ∠WSR ≅ ∠WUT
5. ♠
6. RU || ST; UT || RS
6. converse of alt. interior angles theorem
7. RSTU is a parallelogram
7. def. of a parallelogram