By the definition of a , AD ||BC and AB||DC. Using, AD as a transversal, ZA and are same-

side interior angles, so they are

Using side as a transversal, zB and Care

same-side interior angles, so they are supplementary

Using AB as a transversal, ZA and zB are same-side

interior angles, so they are supplementary

Therefore, ZA is congruent to 2C because they are

supplements of the same angle. Similarly, zB is

congruent to