ABCDis a quadrilateral.P and Q are the mid points of sides CD and AB respectivel. AP and DQ meet at X whereas Bp and CQ meet at Y. Prove that area of ADX+area of BCY=area of quadrilateral PXQY.


given: P and Q are the mid-points of CD and AB respectively.
TPT: area(ADX)+area(BCY)= area of quadrilateral PXQY
proof:
area (ADQ) = area (BDQ).......(1) [since median divides a triangle into two equal areas]
area(ADQ)-area(AQX) = area(BDQ)-area(AQX)
area(ADX) = area(BDQ) - area(AQX).............(2)
similarly
area(BPC) - area(PYC) = area(BPD) - area(PYC)
area(BYC) = area(BPD) - area(PYC)...............(3)
adding eq(2) and eq(3):
area(ADX)+area(BYC) = area(BDQ)+area(BPD) - [area(AQX)+area(PYC)]
= area(BPDQ) - [area(AQX)+area(PYC)............(4)
area(DQP) = area(QPC) [since median divides triangle into equal areas]
similarly :area(PQB) = area(APQ)
area(DQP) + area(PQB) = area(QPC) + area(APQ)
area(QBPD) = area(AQCP)
area(QBY)+area(DXP) = area(AQX)+area(PYC) ............(5)
from eq(4) and eq(5):
area(ADX)+area(BYC) = area(BPDQ) - area(QBY) - area(DXP)
= area of quadrilateral PXQY
hope this helps you.

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