If a circular sheet of perimeter 2πr touching each side of a given quadrilateral sheet of perimeter 2p -Maths 9th

1 Answer

Answer :

Let ABCD be the quadrilateral from which a circular sheet is cut off touching each side of the quadrilateral. Also, given AB + BC + CD + DA = 2p             ...(i) Circumference of the circle = 2πr ⇒ Radius of circle = r ∴ Area of quadrilateral = Area of (ΔOAB + ΔOBC + ΔOCD + ΔODA)= \(rac{1}{2}\) r (AB) + \(rac{1}{2}\) r (BC) + \(rac{1}{2}\) r (CD) + \(rac{1}{2}\) r (DA)= \(rac{1}{2}\) r (AB + BC + CD + DA) = \(rac{1}{2}\) r 2p = pr.∴ Required remaining area = Area of quadrilateral – Area of circle = pr – πr2 = r(p – πr).

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