In the following figure, ABCD is a parallelogram and BC is produced to a point Q such that AD = CQ. If AQ intersect DC at P, then:
area of(△BPC) = area of (△DPQ)
(i)ABCD is a ||gm (given)
(ii)∴ AD =DC
(iii)But AD =CQ (given)
(iv)∴AD=DC=CQ
(v)AD||CQ
(vi)ADQC is a ||gm
(one pair opposite sides are equal and parallel)
(vii)area ΔADC =area Δ(AQD)
(Δ′s in the same base and between the same||'s)
∴ area ΔADP +area ΔAPC =are ΔADP +area ΔDPQ
∴ Area ΔAPC =area ΔDPQ
(viii)area ΔAPC =area ΔBPC(Δ′s in the same base and between the same || lines)
(ix)∴ area ΔAPC =area ΔBPC