Rectangle ABCD circumscribes the circle of radius 10 cm. Prove that ABCD is a square. Hence, find the perimeter of ABCD.

CBSE Class 10 Maths PYQ · Circles · Quad & Circle · 3 Marks · March 2025 · Standard

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1263 Marks · March 2025 · Standard
Rectangle ABCD circumscribes the circle of radius $10$ cm. Prove that ABCD is a square. Hence, find the perimeter of ABCD.
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$AP = AS$
$BP = BQ$
$CR = CQ$
$DR = DS$
Adding the above four equations,
$AP + BP + CR + DR = AS + BQ + CQ + DS$
$\Rightarrow AB + CD = AD + CB$ --- (i)
Since ABCD is a rectangle
$\therefore AB = CD$ and $BC = AD$
$\Rightarrow$ from (i), $2 AB = 2 AD$ or $AB = AD$
Hence ABCD is a square
Clearly side of square = diameter of circle = $20$ cm
$\therefore$ Perimeter of square = $4 \times 20$ cm = $80$ cm
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