Q.

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.


Ans.

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 ABC, we have GFAB

CGGA=CFFB  [By BPT]    ...(1)

In ADC, we have EGDC      (EFAB&ABDC)

DEEA=CGGA  [By BPT]     ...(2)

From (1) & (2), we get, DEEA=CFFB