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ABCD is a rectangle and P, Q, R and S are mid-points of the sides AB, BC, CD and DA respectively. Show that the quadrilateral PQRS is a rhombus.

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Question

ABCD is a rectangle and P, Q, R and S are mid-points of the sides AB, BC, CD and DA respectively. Show that the quadrilateral PQRS is a rhombus.

Sum
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Solution

Let us join AC and BD.

In ΔABC,

P and Q are the mid-points of AB and BC respectively.

∴ PQ || AC and PQ = `1/2 AC`    ...(Mid-point theorem)   ...(1)

Similarly, in ΔADC,

SR || AC and SR = `1/2 AC`        ...(Mid-point theorem)    ...(2)

Clearly, PQ || SR and PQ = SR

Since in quadrilateral PQRS, one pair of opposite sides is equal and parallel to each other, it is a parallelogram.

∴ PS || QR and PS = QR       ...(Opposite sides of the parallelogram)   ...(3)

In ΔBCD, Q and R are the mid-points of side BC and CD respectively.

∴ QR || BD and QR = `1/2 BD`    ...(Mid-point theorem)   ...(4)

However, the diagonals of a rectangle are equal.

∴ AC = BD        …(5)

By using equation (1), (2), (3), (4), and (5), we obtain

PQ = QR = SR = PS

Therefore, PQRS is a rhombus.

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Chapter 8: Quadrilaterals - EXERCISE 8.2 [Page 114]

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NCERT Mathematics [English] Class 9
Chapter 8 Quadrilaterals
EXERCISE 8.2 | Q 3. | Page 114

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