In parallelogram ABCD, two points P and Q are taken on diagonal BD such that DP = BQ (see Fig. 8.20). Show that:


(i) Δ APD Δ CQB


(ii) AP = CQ


(iii) Δ AQB Δ CPD


(iv) AQ = CP


(v) APCQ is a parallelogram

(i) In ΔAPD and ΔCQB,

ADP = CBQ (Alternate interior angles for BC || AD)


AD = CB (Opposite sides of parallelogram ABCD)


DP = BQ (Given)


ΔAPD ΔCQB (Using SAS congruence rule)


(ii) As we had observed that,


ΔAPD ΔCQB


AP = CQ (CPCT)


(iii) In ΔAQB and ΔCPD,


ABQ = CDP (Alternate interior angles for AB || CD)


AB = CD (Opposite sides of parallelogram ABCD)


BQ = DP (Given)


ΔAQB ΔCPD (Using SAS congruence rule)


(iv) As we had observed that,


ΔAQB ΔCPD,


AQ = CP (CPCT)


(v) From the result obtained in (ii) and (iv),


AQ = CP and AP = CQ


Since,


Opposite sides in quadrilateral APCQ are equal to each other,


APCQ is a parallelogram


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