PQ is parallel to TR and PT is parallel to QR.
To Prove: PQT is congruent to RTQ
Proof:In triangles PQT and RTQ, we have
PT = QR (Opp. sides of parallelogram)
PQ = TR (Opp. sides of Parallelogram)
QT = QT (Common)
Therefore,triangle PQT is congruent to triangle RTQ by SSS congruence rule.