Prove that if a line is drawn parallel to one side of a triangle intersecting the other two sides in distinct points, then the other two sides are divided in the same ratio.
Using the above theorem prove that a line through the point of intersection of the diagonals and parallel to the base of the trapezium divides the non parallel sides in the same ratio.
For the Theorem :
Given, To prove, Construction and figure of 1½ marks
Proof of 1½ marks

Let ABCD be a trapezium DCAB and EF is a line parallel to AB and hence to DC.
Join AC, meeting EF in G.
In , we have
...(1)
In , we have ()
...(2)
From (1) & (2), we get,