Diagonals AC and BD of a quadrilateral ABCD intersect each other at P. Show that:

ar(Δ APB) × ar(Δ CPD) = ar(Δ APD) × ar(Δ BPC).

Construction: Draw BQ perpendicular to AC

And,


DR perpendicular to AC


Proof: We have,


L.H.S = Area (ΔAPB) * Area (ΔCPD)


= (AP * BQ) * (PC * DR)


= ( * PC * BQ) * ( * AP * DR)


= Area (ΔBPC) * Area (ΔAPD)


= R.H.S


Therefore,


L.H.S = R.H.S


Hence, proved


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