In Fig. 9.32, ABCD is a parallelogram and BC is produced to a point Q such that AD = CQ. If AQ intersect DC at P, show that ar (BPC) = ar (DPQ)
[Hint: Join AC]
It is given that ABCD is a parallelogram
AD || BC and AB || DC (Opposite sides of a parallelogram are parallel to each other)
Join point A to point C
Consider ΔAPC and ΔBPC
ΔAPC and ΔBPC are lying on the same base PC and between the same parallels PC and AB
Therefore,
Area (ΔAPC) = Area (ΔBPC) (i)
In quadrilateral ACDQ
AD = CQ
Since,
ABCD is a parallelogram
AD || BC (Opposite sides of a parallelogram are parallel)
CQ is a line segment which is obtained when line segment BC is produced
AD || CQ
We have,
AC = DQ and AC || DQ
Hence, ACQD is a parallelogram
Consider ΔDCQ and ΔACQ
These are on the same base CQ and between the same parallels CQ and AD
Therefore,
Area (ΔDCQ) = Area (ΔACQ)
Area (ΔDCQ) − Area (ΔPQC) = Area (ΔACQ) − Area (ΔPQC)
Area (ΔDPQ) = Area (ΔAPC) (ii)
From equations (i) and (ii), we obtain
Area (ΔBPC) = Area (ΔDPQ)