The side of a square is 10 cm. Find

(i) The area of the inscribed circle, and


(ii) The area of the circumscribed circle. [Take π = 3.14.]

(i)


Consider the above figure, Join PR,


Now PR = Diameter of the inscribed circle


Also, PR = BC = 10 cm.


So, PR = 10 cm




r = 5 cm


Area of inscribed circle = πr2 (put value of r in this equation)


Area of inscribed circle = π(52)




Area of inscribed circle = 78.57 cm2


The area of inscribed circle is 78.57 cm2.


(ii)


Consider the above figure, O is the centre of circle and ABCD is a square inscribed. Now OB and OD are radii of circle.


Consider ∆DBC right angled at c (as C is a vertex of square)


Apply Pythagoras theorem in triangle DBC


Hypotenuse2 = Perpendicular2 + Base2


In triangle DBC, hypotenuse = DB,


perpendicular = BC and


base = DC



Put the values of BC and DC i.e. 10 cm



BD2 = 200


BD = √200


BD = 10√2 cm


Now radius of circle = half of BD



r = (10√2)/2


r = 5√2 cm


Hence Area of circumscribing circle = πr2


Area of circumscribing circle = 3.14×5√2×5√2


(put π = 3.14 and r = 5√2 cm)


Area of circumscribing circle = 3.14 × 50


Area of circumscribing circle = 157 cm2


Area of circumscribing circle is 157 cm2.


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