Can we solve this?

Geometry Level 4

In a rectangle ABCD of length 14 and breadth 7, an arc with centre A and radius 14 is drawn. Then the area of shaded region is

4.9 3.9 4.25 8.87

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1 solution

Ishaan Shanker
Oct 30, 2016

n o w , D E = 1 4 2 7 2 = 7 3 a n d a l s o now, DE=\sqrt{14^2-7^2}=7\sqrt{3}\hspace{2mm}and\hspace{2mm}also sin θ = D E / A E = 7 3 / 14 = 3 / 2 a n d \sin\hspace{2mm}\theta=DE/AE=7\sqrt{3}/14=\sqrt{3}/2\hspace{2mm}and θ = 60 s o \theta=60\hspace{2mm}so\hspace{2mm}\implies 90 θ = 90 60 = 30 90-\hspace{2mm}\theta=90-60=30 a r e a o f s e c t o r = π r r θ / 360 = π 14 14 30 / 360 = 51.31 area\hspace{5mm}of\hspace{5mm}sector=\pi*r*r*\theta/360=\pi*14*14*30/360=51.31 a r e a o f A D E = b h / 2 = 7 7 ( 3 ) / 2 = 42.34 area\hspace{5mm}of\hspace{5mm}ADE=b*h/2=7*7\surd(3)/2=42.34 a r e a o f r e c t a n g l e = l b = 14 7 = 98 area\hspace{5mm}of\hspace{5mm}rectangle=l*b=14*7=98 a r e a o f s h a d e d r e g i o n = a r r e c t a n g l e ( a r s e c t o r + a r A D E ) = 98 ( 51.31 + 42.43 ) = 98 93.74 = 4.26 area\hspace{5mm}of\hspace{5mm}shadedregion=ar rectangle-(ar sector+ar ADE)=98-(51.31+42.43)=98-93.74=4.26

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