Areas?

Let the center of the square be $O$ and let the midpoint of side $CD$ be $P$ . Also, define $R$ as the region bounded by the arc $OC$ and the line segment $OC$ . By symmetry, the area of the shaded region will be $8$ times the area of $R$ .

Now the area of $R$ is the area of sector $OPC$ , (a quarter-circle), minus the area of triangle $\Delta OPC$ . Thus the area of $R$ is

$\dfrac{1}{4}\pi*(PC)^{2} - \dfrac{1}{2}(PC)(OP) = \dfrac{25}{4}*3.14 - \dfrac{1}{2}*25 = \dfrac{25}{4}*(3.14 - 2) = 7.125.$

The area of the shaded region is then $8*7.125 = \boxed{57}$ .

We can use this expression for all question like this :
Shaded area =

So → Shaded area= 2(25)(3.14-2)=57 :)