Question 1029427
If you draw this, the side of the square on the diameter is symmetric from the center, and let each part be x.
But the sides are now 2x each, so the vertical sides, extending to the semicircle, are 2x.  The diagonal is the radius, or 5 cm.  That is a right triangle.
x^2+(2x)^2=5^2=25
5x^2=25
x^2=5
x= +sqrt(5) cm.
2x= 2sqrt(5) cm.
The area of the square is twice x or [2(sqrt(5)]^2=4*5=20 cm^2