P is any point on the diagonals AC of a parallelogram ABCD.Prove that ar(△ADP)=ar(△ABP).
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Solution
Join BD. Let BD and AC intersect at point O. O is thus the midpoint of DB and AC. PO is the median of △△DPB, So, ar(△DPO)=ar(△BPO) .....(1) ar(△ADO)=ar(△ABO) .....(2) Case 1: (2)−(1) ⇒ar△ADO-ar△DPO=ar△ABO-ar△BPO Thus, ar(∆ADP) = ar(∆ABP) Case II: