Seeing that the radius is 2m, we also see that the diameter is 4m. Looking at the picture, the height of the triangle is also 4m. Given that the shape around the circle is a square, we now know the dimensions of the square is 4m x 4m. Knowing that a triangle with such symmetry is half the area of the square, we calculate it as (4 x 4) / 2 = 8m^2, which is your answer.
