Non shadow part (white one) seems to be 1/4 of a circumference
So we need to find area of square minus area of 1/4 of the circumference
Square area = L^2 = 6^2 = 36
Circumference Area = (πr^2)/4 = (π*6^2)/4 = 28.27
Area of the shaded portion = 36 - 28.27 = 7.72