Question

11. In A ABC and A DEF, AB =DE, AB || DE, BC = EF and BC II EF. Vertices A, B and C are joined to vertices D, E and F respectively (see Fig. 8.22). Show that ) (i) quadrilateral ABED is a parallelogram (ii) quadrilateral BEFC is a parallelogram (ii) AD II CF and AD=CF (iv) quadrilateral ACFD is a parallelogram (v) AC=DF (vi) A ABC=A DEF​

Answer 1

(i) Consider the quadrilateral ABED

We have , AB=DE and AB∥DE

One pair of opposite sides are equal and parallel. Therefore

ABED is a parallelogram.

(ii) In quadrilateral BEFC , we have

BC=EF and BC∥EF. One pair of opposite sides are equal and parallel.therefore ,BEFC is a parallelogram.

(iii) AD=BE and AD∥BE ∣ As ABED is a ||gm ... (1)

and CF=BE and CF∥BE ∣ As BEFC is a ||gm ... (2)

From (1) and (2), it can be inferred

AD=CF and AD∥CF

(iv) AD=CF and AD∥CF

One pair of opposite sides are equal and parallel

⇒ ACFD is a parallelogram.

(v) Since ACFD is parallelogram.

AC=DF ∣ As Opposite sides of a|| gm ACFD

(vi) In triangles ABC and DEF, we have

AB=DE ∣ (opposite sides of ABED

BC=EF ∣ (Opposite sides of BEFC

and CA=FD ∣ Opposite. sides of ACFD

Using SSS criterion of congruence,

△ABC≅△DEF