The diagonal divides a parallelogram into two congruent triangles. In a parallelogram opposite sides are equal and conversely. In a parallelogram opposite angles are equal and conversely. A quadrilateral is a parallelogram if a pair of its opposite sides is parallel and equal. In a parallelogram, the diagonals bisect each other and conversely.
9.G.Q.2
In a triangle, the line segment joining the mid points of any two sides is parallel to the third side and (motivate) its converse.
