I've tried to find the area of the shaded region in the image bellow knowing that we have a square of side 20, and I found $A=50\left ( \sqrt{7} + \arccos\left ( \frac{-3}{4} \right )-4\arccos\left ( \frac{9}{16} \right ) \right )$, after alot of trigonometry ... I wanna know if my solution is correct and if there is another easy way to solve this problem, thanks in advance.
