Area

Geometry Level pending

A 12 feet diameter circle is divided into two parts by chord A. The perpendicular distance of chord A from the center of the circle is two feet. Find the area of the bigger part.

81.1 feet² 82.1 feet² 79.1 feet² 80.1 feet²

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1 solution

Consider the figure above. The area of the bigger part is area of the circle minus the area of the segment.

cos ϕ = 2 6 \cos \phi=\dfrac{2}{6} \implies ϕ = cos 1 ( 2 6 ) 70.529 \phi=\cos^{-1}\left(\dfrac{2}{6}\right) \approx70.529 \implies 2 ϕ = 2 ( 70.529 ) 141.058 2\phi=2(70.529) \approx 141.058

A b i g g e r p a r t = A c i r c l e A s e g e m e n t = π ( 6 2 ) [ 141.058 360 π ( 6 2 ) 1 2 ( 6 2 ) ( sin 141.058 ) ] A_{bigger~part}=A_{circle}-A_{segement}=\pi(6^2)-\left[\dfrac{141.058}{360}\pi (6^2)-\dfrac{1}{2}(6^2)(\sin~141.058)\right] \approx 80.01 \boxed{80.01}

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