keshav kumar
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In parallelogram ABCD, two points P and Q are taken on diagonal BD such that DP = BQ see Figure. Show that: (i) ∆ APD ≅ ∆ CQB (ii) AP = CQ (iii) ∆ AQB ≅∆ CPD (iv) AQ = CP (v) APCQ is a parallelogram

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Opposite angles in a parallelogram, why are congruent.
To prove is a diagonal of parallelogram.
Class 9th Maths, Page No:147, Questions No:9, Exercise 8.1
NCERT, Solutions for Class 9th Maths, Session 2023-2024.

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1 Answer

  1. (i) In ΔAPD and ΔCQB,
    DP = BQ [∵ Given]
    ∠ADP = ∠CBQ [∵ Alternate angle]
    AD = BC [∵ Opposite sides of a parallelogram]
    Hence, ΔAPD ≅ ΔCQB [∵ SAS Congruency rule]

    (ii) ΔAPD ≅ CQB [∵ Prove above]
    AP = CQ …(1) [∵ CPCT]

    (iii) In ΔAQB and ΔCPD,
    QB = DB [∵ Given]
    ∠ABQ = ∠CDP [∵ Alternate angle]
    AB = CD [∵ Opposite sides of a parallelogram]
    Hence, ΔAQB ≅ ΔCPD [ SAS Congruency rule]

    (iv) ΔAQB ≅ ΔCPD [∵ Prove above]
    AQ = CP …(2) [∵ CPCT]

    (v) In APCQ,
    AP = CQ [∵ From (1)]
    AQ = CP [∵ From (2)]
    The opposite sides of quadrilateral APCQ are equal.
    Hence, APCQ is a parallelogram.

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