Given: rt ≅ tv and st ≅ tu prove: rsvu is a parallelogram. statements reasons 1. rt ≅ tv; st ≅ tu 1. given 2. ∠rts and ∠vtu are vert. ∠s; ∠rtu and ∠vts are vert. ∠s 2. definition of vertical angles 3. ∠rts ≅ ∠vtu; ∠rtu ≅ ∠vts 3. vertical angles are congruent 4. ? 4. sas congruency theorem 5. ∠vrs ≅ ∠rvu; ∠usr ≅ ∠suv; ∠vru ≅ ∠rvs; ∠rus ≅ ∠usv 5. cpctc 6. ∠vrs and ∠rvu, ∠usr and ∠suv, ∠vru and ∠rvs, ∠rus and ∠usv are each a pair of alternate interior angles 6. definition of alternate interior angles 7. rs ∥ uv and ru ∥ sv 7. converse of the parallelogram diagonal theorem 8. rsvu is a parallelogram 8. definition of parallelogram what is the missing statement in step 4?