Answer:
1: DO = OB, AO = OC 1: Given
2: DOC = AOB 2: Vertical angles are equal.
3: Triangle COD congruent to Triangle AOB 3: SAS
4: 1 = 2, AB = DC 4: CPCTE
5: AB||DC 5: If alternate interior angles =, then lines parallel.
6: ABABCD is a parallelogram 6: If two sides = and ||, then a parallelogram.
I just had this question on my lesson, the answers are right! Goodluck! :)