Answer:
Actually, there are two. They are the Parallelogram Opposite Sides Theorem and the Parallelogram Opposite Angles Theorem.
Step-by-step explanation:
POST means that if opposite sides of a quadrilateral are the same, it's a parallelogram.
POAT means that if opposite sides of a quadrilateral are the same, it's a parallelogram.
A quadrilateral has to meet both of these theorems to be a parallelogram.
