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P, Q, R and S are respectively the mid-points of the sides AB, BC, CD and DA of a quadrilateral ABCD such that AC ⊥ BD. Prove that PQRS is a rectangle. - Mathematics

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P, Q, R and S are respectively the mid-points of the sides AB, BC, CD and DA of a quadrilateral ABCD such that AC ⊥ BD. Prove that PQRS is a rectangle.

Sum

Solution


Given, P, Q, R and S are mid-points of the sides AB, BC, CD and DA, respectively.

Also, AC is perpendicular to BD

∠COD = ∠AOD = ∠AOB = ∠COB = 90°

In ΔADC, by mid-point theorem,

SR || AC and SR = `1/2` AC

In ΔABC, by mid-point theorem,

PQ || AC and PQ = `1/2` AC

∴ PQ || SR and SR = PQ = `1/2` AC

Similarly, SP || RQ and SP = RQ = `1/2` BD

Now, in quadrilateral EOFR,

OE || FR, OF || ER

∠EOF = ∠ERF = 90°

Hence, PQRS is a rectangle.

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Chapter 8: Quadrilaterals - Exercise 8.4 [Page 82]

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NCERT Exemplar Mathematics [English] Class 9
Chapter 8 Quadrilaterals
Exercise 8.4 | Q 4. | Page 82

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