According to the given information, segment AB is parallel to segment DC and segment BC is parallel to segment AD . Using a straightedge, extend segment AB and place point P above point B. By the same reasoning, extend segment AD and place point T to the left of point A. Angles BCD and PBC are congruent by the Alternate Interior Angles Theorem. Angles PBC and BAD are congruent by the . By the Transitive Property of Equality, angles BCD and BAD are congruent. Angles ABC and BAT are congruent by the . Angles BAT and CDA are congruent by the Corresponding Angles Theorem. By the Transitive Property of Equality,∠ ABC is congruent to∠ CDA. Consequently, opposite angles of parallelogram ABCD are congruent.