If E, F, G and H are respectively the mid-points of the sides of a parallelogram ABCD, show that ar(EFGH) = ar(ABCD).
[Hint. Through P, draw a line parallel to AB.]
In figure, PQRS and ABRS are parallelograms and X is any point on side BR. Show that:
(i) ar(|| gm PQRS) = ar(|| gm ABRS)
(ii)
In ΔAOP and ΔCOQ,
AO = CO
| ∵ Diagonals of a parallelogram bisect each other
∠AOP = ∠COQ
| Vertically opposite angles ∠OAP = ∠OCQ
| Alternate interior angles ∴ ΔAOP = ΔCOQ
| By ASA Congruence Rule ∴ ar(ΔAOP) = ar(ΔCOQ)
| ∵ Congruent figures have equal areas ⇒ ar(ΔAOP) + ar(□OPDC)
= ar(ΔCOQ) + ar(□OPDC)
⇒ ar(ΔACD) = ar(□PDCQ)
⇒ 1/2 ar(|| gm ABCD) = ar(□PDCQ)
| From (1) ⇒ ar(□PQBA) = ar(□PDCQ)
⇒ ar(□PDCQ) = ar(□PQBA).