(1) Triangle proportionality theorem:
If a line parallel to one side of a triangle intersects the other two sides of the triangle, then the line divides these two sides proportionally
That is, if BE is parallel to AC, then DE divides AB and BC proportionally
(2) Converse of the Triangle proportionality Theorem:
if a line divides two sides of a triangle proportionally, then it is parallel to the third side.
That is , if DE divides AB and BC proportionally, Then DE is parallel to AC