Question

if ABCD IS A PARALLELOGRAM THE PROVE THAT

Answer 1

plz go to CBSE mathematics textbook of 9th class chapter 9 and exercises 9.3 questions no. 2

Answer 2

in ΔABC and ΔADC,
(i) AB =CD (opposite sides of ║gm)
(ii) AD = BC(opposite sides of ║gm)
(iii) AC is common.
 ∴ ΔABC ≈ ΔADC

similarly,
in ΔABD andΔBCD,
(i) AD =BC
(ii) AB=DC
(iii) BD is common

now ar(║gm ABCD)= ar(ΔABD) + ar(ΔBCD)
⇒ ar(║gm) =2ar(ΔABD)
∴
ar(ΔABC)=ar(ΔBCD)=ar(ΔADC)=ar(ΔABD)= $\frac{1}{2} ar($║gm ABCD)