Shaded Area: Leaf in a Square

Explanations

1. Two unshaded parts can be spotted in the square - up-right and down-left. Each of them is the difference between the square’s area and the 90-degree circle segment with the radius of 8.

2. The area of the 90-degree circle segment is 1/4 of the full circle with the radius of 8. I.e.: 1/4 * pi * r^2 = 1/4 * pi * 64 = 16 * pi = 50.24.

3. The difference between square’s area and (2): 8 * 8 - 50.24 = 64 - 50.24 = 13.76.

4. There are two unshaded parts in the square. Their total area: 2 * 13.76 = 27.52.

5. The are of the shaded part is the difference between the square’s area and (4): 8 * 8 - 27.52 = 64 - 27.52 = 36.48.