The area of the region, inside the circle (x−23)2+y2=12 and outside the parabola y2=23x is
(A)6π−8
(B)3π−8
(C)6π−16✓ Correct
(D)3π+8
Answer: (C)
Solution
The circle (x−23)2+y2=12 has center (23,0) and radius 23, so it passes through the origin. The parabola y2=23x also passes through the origin, and substituting into the circle equation:
(x−23)2+23x=12⟹x2−43x+12+23x=12⟹x2−23x=0⟹x=0 or x=23.
So the curves meet at x=0 and x=23 — the parabola's arc lies inside the circle between these two intersections, and the full circle has area π(23)2=12π, split into two halves by symmetry about the x-axis with the chord through the intersection points.
Required area = area of circle to the right of the chord at x=23 (a semicircle) minus the area between the parabola and this chord line, doubled for symmetry above and below the axis:
Area=2πr2−2∫02323xdx,
where 2πr2=2π(12)=6π is the semicircular area beyond the chord x=23, and the second term is the area under the parabola from x=0 to x=23 (doubled for both branches ±y).