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In a parallelogram ABCD, E and F are the mid-points of sides AB and CD respectively see Figure. Show that the line segments AF and EC trisect the diagonal BD.

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Define vertically opposite angles.
Prove to corresponding sides of similar triangles
Class 9, EXERCISE 8.2, Page No: 151, Questions No:5.
Session 2023-2024 are based on CBSE Board.

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1 Answer

  1. In quadrilateral ABCD,
    AB = CD [∵ Given]
    (1/2)AB = (1/2)CD
    ⇒ AE = CF [∵ E and F are the mid-points of AB and CD respectively]
    In Quadrilateral AECF,
    AE = CF [∵ Proved above]
    AE ∥ CF [∵ Opposite sides of a parallelogram]
    Hence, AECF is a parallelogram.
    In ΔDCQ,
    F is mid-point of DC [∵ Given]
    and FP ∥ CQ [∵ AECF is a Parallelogram]
    Hence, P is mid-point of DQ [ Converse of mid-point theorem]
    Hence, DP = PQ …(1)
    Similarly,
    In ΔABP,
    E is mid-point of AB [∵ Given]
    and EQ ∥ AP [∵ AECF is a parallelogram]
    Hence, Q is mid-point of PB [∵ Converse of mid-Point Theorem]
    Hence, PQ = QB …(2)
    From (1) and (2), we have
    DP = PQ = QB
    Hence, line segment AF and EC trisect BD.

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