Explanation:
We first calculate the lenght of the diameter, that is also the lenght of the hypotenuse of the right triangle shown in the figure:
d =
cm
The radius of the circle will be half of the diameter: r = d/2 = 2.5 cm
The area of the circle will be: Acircle = pi * r^2 = pi * 6.25 cm^2 = 19.6 cm^2 (circa).
Now from the area of the circle we subtract the area of the square:
Asquare = 4cm * 3cm = 12cm^2
A shaded = Acircle - Asquare = 19.6 cm^2 - 12cm^2 = 7.6 cm^2