In Figure, `A B C D` is a parallelogram and `E F C D` is a rectangle. Also `A L\ _|_D C`. Prove that
(i) `a r(A B C D=a r(E F C D)`
(ii) `a r\ ( A B C D)=D C` x `A L`

Explanation

As per the given figure, both `ABCD` and `EFCD` lies on the same parallel line `EB` and have common base `CD`.

We know, if two parallelograms lie on the same parallel line and have a common base, then they have equal area.

Thus, `ar(ABCD) = ar(EFCD)`

Also, we can say that ,
`ar(ABCD) = ar(EFCD) = DCxxDE`

As, `AL` is a perpendicular to `CD` in rectangle `EFCD`,

`AL=DE`

So, `ar(ABCD) =DCxxAL`