设该圆的半径为R.
内接六边形包括六个 边长等于R的等边三角形.
内接六边形的面积 = 6 R^2 sin60°/2
6 R^2 sin60° = 6√3/2
R^2 × √3/2 = 6√3/2
R^2 = 6
R = √6