In the given figure, ABCD is a quadrilateral. A line through 'D', parallel to AC, meets BC produced in P. Then:
Here ΔDAC and ΔPAC are on the same base AC and between parallel lines AC and DP
⇒ Area (ΔDAC) = Area (ΔPAC)
Adding Area (ΔACB) on both sides, we have,
⇒ Area (ΔDAC) + Area (ΔACB)
= Area (ΔPAC) + Area (ΔACB)
⇒Area(quadABCD)=Area(ΔAPB)