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ABCD is a rectangle in which diagonal BD bisects ∠B. Show that ABCD is a square. - Mathematics

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Question

ABCD is a rectangle in which diagonal BD bisects ∠B. Show that ABCD is a square.

Sum

Solution

Given: In a rectangle ABCD, diagonal BD bisects ∠B.

Construct: Join AC.

To show: ABCD is a square.


Proof: In ΔBAD and ΔBCD, 

∠ABD = ∠CBD   ...[Given]

∠A = ∠C  ...[Each 90°]

And BD = BD   ...[Common side]

∴ ΔBAD ≅ ΔBCD   ...[By AAS congruence rule]

∴ AB = BC

And AD = CD  [By CPCT rule]  ...(i)

But in rectangle ABCD, opposite sides are equal.

∴ AB = CD

And BC = AD  ...(ii)

From equations (i) and (ii),

AB = BC = CD = DA.

So, ABCD is a square.

Hence proved.

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Chapter 8: Quadrilaterals - Exercise 8.4 [Page 83]

APPEARS IN

NCERT Exemplar Mathematics [English] Class 9
Chapter 8 Quadrilaterals
Exercise 8.4 | Q 15. | Page 83
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