ABCD is a parallelogram whose diagonals intersect at O. If P is any point on BO, prove that
(i)    ar(ΔADO) = ar(ΔCDO)
(ii)    ar(ΔABP) = ar(ΔCBP)
Given: ABCD is a parallelogram whose diagonals intersect at O. P is any point on BO.
To Prove:
(i) ar(ΔADO) = ar(ΔCDO) (ii) ar(ΔABP) = ar(ΔCBP)
Proof:
(i)    ∵ Diagonals of a parallelogram bisect each other
∴ AO = OC
⇒ O is the mid-point of AC
DO is a median of ΔDAC
ar(ΔADO) = ar(ΔCDO)
∵ A median of a triangle divides it into two triangles of equal areas
(ii)    ∵ BO is a median of ΔBAC
∴ ar(ΔBOA) = ar(ΔBOC)    ...(1)
∵ A median of a triangle divides it into two triangles of equal areas ∵ PO is a median of ΔPAC
∴ ar(ΔPOA) = ar(ΔPOC)    ...(2)
∵ A median of a triangle divides it into two triangles of equal areas Subtracting (2) from (1), we get ar(ΔBOA) – ar(ΔPOA) = ar(ΔBOC) – ar(ΔPOC) ⇒    ar(ΔABP) = ar(ΔCBP)