Bunuel

In the figure, ARD is an arc of a circle centered at point O, ABCD is a rectangle, and CD = a/2. What is the area of the shaded region?
A. \((\frac{\sqrt{2}}{2} - \frac{1}{2})a^2\)
B. \((\frac{\sqrt{2}}{2} - \frac{\pi}{4})a^2\)
C. \((\frac{\sqrt{2}}{2} - \frac{\pi}{4} - \frac{1}{2})a^2\)
D. \((\frac{\sqrt{2}}{2} + \frac{\pi}{4} - \frac{1}{2})a^2\)
E.\((\frac{\sqrt{2}}{2} - \frac{\pi}{4} + \frac{1}{2})a^2\)
Area of shaded region = Area of rectangle - Area of segment ARDA
Area of rectangle = lb = \((\frac{a}{2}*\sqrt{2}a) = \frac{\sqrt{2}}{2}*a^2\)
Area of segment ARDA = Area of sector OARDO - Area of triangle OAD
Area of segment ARDA = \(\frac{1}{4}*\pi*a^2 - \frac{1}{2}*a^2\)
Area of shaded region = \(\frac{\sqrt{2}}{2}*a^2 - (\frac{1}{4}*\pi*a^2 - \frac{1}{2}*a^2)\)
Area of shaded region =\(a^2 * (\frac{\sqrt{2}}{2} - \frac{1}{4}*\pi + \frac{1}{2})\)
Answer (E)