to complete the proof of the following theorem. If a quadrilateral is a parallelogram, then its opposite angles are congruent. By definition, a parallelogram is a quadrilateral in which both pairs of opposite sides are parallel. Use this definition in your proof. B C Given: ABCD is a parallelogram Prove: ZALC A Statement D Reason 1 ABCD is a parallelogram Given 2 AB || 3 AD || 4 ZA and are supp. angles 5 ZA and are supp. angles 6 ZB40 7 ZC and are supp. angles L 8 ZAZC Definition of a Parallelogram Definition of a Parallelogram Reason? Reason? Ifs are supp. to the same Z, they are Reason? Reason? 12