1. Draw perpendicular bisectors of AB, BC, and AC, which intersects each other at G. Point G is equidistant from the three vertices of ΔABC.

    Draw perpendicular bisectors of AB, BC, and AC, which intersects each other at G.
    Point G is equidistant from the three vertices of ΔABC.

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  2. Draw the bisectors of ∠A, ∠B and ∠C, which intersect each other at O. Point O is equidistant from the three sides of ΔABC ie. OP = OQ = OR.

    Draw the bisectors of ∠A, ∠B and ∠C, which intersect each other at O. Point O is equidistant from the three sides of ΔABC ie. OP = OQ = OR.

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  3. In ΔABC, P is mid-point to AB [∵ Given] Q is mid-point of BC [∵ Given] Hence, PQ ∥ AC and PQ = (1/2)AC ... (1) [∵ Mid-point Theorem] Similarly, in ΔACD, S is mid-point of AD [∵ Given] R is mid-point of CD [∵ Given] Hence, SR ∥ AC and SR = (1/2) AC ...(2) [∵ Mid-Point Theorem] From (1) and (2), we haRead more

    In ΔABC,
    P is mid-point to AB [∵ Given]
    Q is mid-point of BC [∵ Given]
    Hence, PQ ∥ AC and PQ = (1/2)AC … (1) [∵ Mid-point Theorem]

    Similarly, in ΔACD,
    S is mid-point of AD [∵ Given]
    R is mid-point of CD [∵ Given]
    Hence, SR ∥ AC and SR = (1/2) AC …(2) [∵ Mid-Point Theorem]

    From (1) and (2), we have
    PQ ∥ SR …(3) [∵ PQ ∥ AC and SR ∥ AC]
    and PQ = SR …(4) [∵ SR = (1/2)AC and PQ = (1/2)AC]

    Hence, PQRS is a parallelogram.

    Similarly, in ΔBCD,
    Q is mid-point of BC [∵ Given]
    R is mid-point of CD [∵ Given]
    Hence, QR = (1/2) BD …(5) [∵ Mid-point theorem]
    Given that: AC = BD …(6) [∵ Diagonals of a rectangle are equal]
    From (1), (5) and (6), we have
    PQ = QR
    A parallelogram whose adjacent sides are equal, is a rhombus. Hence, PQRS is a rhombus.

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  4. In ΔACD, S is mid-point to DA [∵ Given] R is mid-point of DC [∵ Given] Hence, SR ∥ AC and SR = (1/2)AC ... (1) [∵ Mid-point Theorem] In ΔACD, P is mid-point of AB [∵ Given] Q is mid-point of BC [∵ Given] Hence, PQ ∥ AC and PQ = (1/2) AC ...(2) [∵ Mid-Point Theorem] From (1) and (2), we have PQ ∥ SRRead more

    In ΔACD,
    S is mid-point to DA [∵ Given]
    R is mid-point of DC [∵ Given]
    Hence, SR ∥ AC and SR = (1/2)AC … (1) [∵ Mid-point Theorem]

    In ΔACD,
    P is mid-point of AB [∵ Given]
    Q is mid-point of BC [∵ Given]
    Hence, PQ ∥ AC and PQ = (1/2) AC …(2) [∵ Mid-Point Theorem]

    From (1) and (2), we have
    PQ ∥ SR …(3) [∵ PQ ∥ AC and SR ∥ AC]
    and PQ = SR …(4) [∵ SR = (1/2)AC and PQ = (1/2)AC]
    In quadrilateral PQRS,
    PQ ∥ SR and PQ = SR [∵ From (3) and (4)]
    Hence, PQRS is a parallelogram and diagonals of parallelogram bisect each other.
    Therefore, SQ and PR bisects each other.

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  5. (i) In ΔABC, M is mid-point to AB [∵ Given] and DM ∥ BC [∵ Given] Hence, D is mid-point of AC [∵ Converse of Mid-point Theorem] (ii) ∠ADM = ∠ACB [∵ Corresponding angles] ⇒ ∠ADM = 90° [∵ ∠ACB 90°] Hence, MD ⊥ AC (iii) In ΔAMD = ΔCMD, AD = DC [∵ Proved above] ∠ADM = ∠CDM [∵ Each 90°] DM = DM [∵ CommonRead more

    (i) In ΔABC,
    M is mid-point to AB [∵ Given]
    and DM ∥ BC [∵ Given]
    Hence, D is mid-point of AC [∵ Converse of Mid-point Theorem]

    (ii) ∠ADM = ∠ACB [∵ Corresponding angles]
    ⇒ ∠ADM = 90° [∵ ∠ACB 90°]
    Hence, MD ⊥ AC

    (iii) In ΔAMD = ΔCMD,
    AD = DC [∵ Proved above]
    ∠ADM = ∠CDM [∵ Each 90°]
    DM = DM [∵ Common]
    Hence, ΔAMD ΔCMD [∵ SAS Congruency rule]
    AM = CM [∵ CPCT]
    But AM = (1/2) AB [∵ Given]
    Therefore, CM = AM = (1/2) AB

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